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Ransomware that combines robust encryption with rapid lateral movement significantly increases the risk and impact of an attack. The Gentlemen ransomware is a ransomware-as-a-service (RaaS) threat that is distinguished by its ability to pair its strong per-file encryption with an aggressive self-propagation capability designed to enable broad network compromise. In addition to using per-file ephemeral Curve25519 keys with XChaCha20 stream cipher, The Gentlemen ransomware attempts to spread across an environment using series of simultaneous, distinct lateral movement methods, increasing the likelihood of widespread impact once initial access is achieved.

Microsoft Threat Intelligence tracks the operators behind the ransomware as Storm-2697, a financially motivated threat actor that manages the RaaS platform known as “The Gentlemen” while affiliates carry out attacks. Emerging around mid-2025, The Gentlemen initially started as a closed ransomware group then began offering its RaaS to affiliates in September 2025. More recently, The Gentlemen operators established an official partnership with BreachForums, a popular cybercriminal marketplace, to recruit affiliates including penetration testers and initial access brokers. Given that The Gentlemen is already a widely adopted RaaS platform, this partnership may lead to increased activity as the program becomes accessible to a broader pool of threat actors.

The operators behind the ransomware use double extortion tactics, encrypting data while also exfiltrating sensitive information to pressure victims through the threat of public release if the ransom is not paid. The ransomware is written in Go and obfuscated with Garble to target the Windows environment. Microsoft has observed The Gentlemen ransomware impacting organizations across education, transportation, healthcare, and financial industries in North America, South America, Europe, Africa, and Asia.

In this blog, we present a detailed analysis of the Gentlemen ransomware encryptor, including its execution flow, defense evasion behaviors, encryption design, and lateral movement techniques. This research is intended to provide defenders, incident responders, and the broader security community with a better understanding of how the threat operates, from initial argument parsing and defense evasion, through its file encryption internals, to the full lateral movement that enables it to propagate across the network. We also provide mitigation guidance, Microsoft Defender detections, hunting queries, and indicators of compromise (IOCs) to help organizations defend against this threat and similar ransomware activity.

Pre-encryption

Command-line argument processing

The ransomware operator can control The Gentlemen encryptor through command-line arguments. A password is required for execution, and optional arguments allow the operator to specify encryption scope, speed, lateral movement, and post-encryption behaviors.

The binary accepts the following arguments:

The --full command-line argument appears to be the intended mode of operation for comprehensive file encryption on the infected device. When this argument is provided, the malware spawns two child processes of itself: one appended with the argument --system to encrypt local volumes under a SYSTEM-privileged scheduled task, and one appended with the argument --shares to encrypt network shares. This separation ensures that the malware can reach both local drives (which might require SYSTEM privileges) and mapped network shares (which are only visible in the user’s session).

The speed arguments (--fast, --superfast, --ultrafast) are mutually exclusive and control how much of each large file is encrypted. When no speed flag is specified, the default per-chunk percentage is 9%. These flags only affect files that are larger than 1 MB, and small files are fully encrypted regardless of the speed setting.

Usage prompt

When the encryptor is executed with no command-line argument, the malware prints a branded usage banner to the console.

It first executes the following PowerShell commands to render a console header:

This is followed by a detailed usage prompt provided by the malware author that documents all available flags with descriptions and examples:

It is worth noting that the file size percentages listed in the usage prompt refer to the total file encryption amount. Internally, the malware encrypts three separate chunks, and the per-chunk percentage used in the code is: fast=3%, superfast=1%, ultrafast=0.3%, default=9%.

Password check

Before executing its primary functionality, the malware validates the --password argument against a hardcoded value embedded within the binary. For the sample analyzed in this blog, the expected password is “9VoAvR7G”. If the provided password does not match, the malware outputs bad args and terminates execution.

This password check is a simple operator authentication mechanism, with each build containing a unique embedded password. Its purpose is to restrict execution to authorized operators and reduce the risk of accidental or unauthorized detonation if the binary is recovered or intercepted. However, because this validation relies on a static comparison, it can be easily identified and bypassed through static analysis techniques.

System encryption: Privilege escalation

When the --system argument is provided (either directly or via the --full argument), the malware creates a scheduled task to re-execute itself as SYSTEM. If a delay value is also specified through the --T argument, the scheduled execution time is adjusted accordingly.

To relaunch itself as SYSTEM, it issues the following sequence of commands:

The malware can only perform this task if it’s executed from an account with administrator privilege. It first deletes any existing task named gentlemen_system to avoid conflicts, creates a new one-time task that runs its binary under the SYSTEM account, and finally triggers that task.

This sequence ensures a clean state by first removing any existing task with the same name (gentlemen_system), creating a new scheduled task that executes the ransomware binary with SYSTEM-level privileges before finally triggering its immediate execution.

When running within this scheduled task context, the malware sets the environment variable LOCKER_BACKGROUND=1. This variable functions as an internal execution flag, indicating that the process is operating as a background encryption worker with elevated privileges, rather than as the original operator-invoked instance.

Defense evasion

Before starting file encryption, the malware executes a sequence of commands to disable defensive controls and remove potential forensic artifacts.

Disable Microsoft Defender

The PowerShell commands disable Microsoft Defender real-time monitoring to remove active protection on the infected device. The malware then adds its own executable to the Defender exclusion list to avoid detection. Finally, it excludes the entire C:\ volume from scanning, reducing the likelihood of subsequent detection during file encryption.

Delete shadow copies and event logs

To further impede recovery efforts, the malware deletes all Volume Shadow Copies using both vssadmin and wmic (Windows Management Instrumentation command-line utility). It then clears the System, Application, and Security event logs using wevtutil to remove key audit trails.

Delete forensics artifacts

These commands remove a variety of forensic artifacts, including prefetch files that track program execution, Defender diagnostic and support logs, and Remote Desktop Protocol (RDP) logs.

Additionally, the malware manually deletes PowerShell command history across all user profiles by removing the following file:

This action eliminates evidence of previously executed PowerShell commands, further reducing the visibility of execution history and threat actor activity.

Process and service termination

Process termination

The malware stops a list of running processes using the command:

The table below summarizes the different categories and processes being targeted:

Service termination

In addition to terminating processes, the malware disables and stops a list of Windows services using the commands:

The table below summarizes the different categories and services being targeted:

Terminating these processes and services serves two primary objectives:

• File access and encryption reliability: Many targeted processes/services, such as databases, Office applications, and backup agents, maintain active file locks. By forcibly terminating these processes, the ransomware ensures that locked files become accessible for encryption.
• Defense and recovery disruption: By stopping backup services, endpoint protection agents, and remote access tools, the malware reduces the likelihood of real-time detection and data restoration from backups.

Collectively, these behaviors maximize encryption coverage while hindering the environment’s ability to detect, respond to, or recover from the attack.

Persistence

The encryptor can establish persistence for itself through two mechanisms: scheduled tasks and registry keys.

Scheduled tasks persistence

For establishing persistence with scheduled tasks, the malware executes the following sequence of commands:

These commands first remove any pre-existing tasks with the same names, then create two persistence mechanisms that execute automatically at system startup. The UpdateSystem task launches the payload in the SYSTEM security context, while the UpdateUser task launches it in the currently signed-in user’s context. This design increases the likelihood that the ransomware will run after reboot regardless of privilege level or sign-in state.

Registry keys persistence

For establishing persistence with the registry, the malware executes the following sequence of commands:

The GupdateS value under HKEY_LOCAL_MACHINE (HKLM) provides device-wide persistence that allows the malware to run at startup for all users, while the GupdateU value under HKEY_CURRENT_USER (HKCU) provides user-scoped persistence within the current profile. By writing to both registry hives, the malware establishes redundant autorun paths across both system-level and user-level execution contexts.

Together, the scheduled tasks and Run key modifications create layered persistence, ensuring that the encryptor is re-executed after a reboot in both privileged and user-context scenarios.

Network share traversal

When the command-line argument --shares is provided, the malware initiates network share discovery and enumeration. It begins by probing all drive letters A through Z to identify mapped network drives using the following commands:

This sequence discovers any drives that are already mapped in the current user’s session, which are then added to the encryption target list.

To further enhance visibility into the network environment, the malware enables multiple Windows network discovery services and their associated firewall rules using the following commands:

The services enabled as part of this process include:

• Function Discovery Resource Publication (fdrespub): Publishes the host’s resources to the network, allowing other systems to detect it.
• Function Discovery Provider Host (fdPHost): Hosts provider components responsible for discovering network resources.
• Simple Service Discovery Protocol (SSDP) Discovery (SSDPSRV): Enables discovery of Universal Plug and Play (UPnP) devices.
• UPnP Device Host (upnphost): Supports the hosting and management of UPnP devices.

Finally, the malware reinforces this configuration by enabling the Network Discovery firewall rule group. This redundancy ensures that firewall restrictions do not limit its network visibility, further maximizing the number of reachable targets for encryption and propagation.

Volume and directory traversal

To enumerate all available volumes on the system, the malware executes the following PowerShell command sequence:

This command queries Windows Management Instrumentation (WMI) for all mounted volumes with drive letter paths and attempts to enumerate Cluster Shared Volumes (CSVs).

Additionally, the malware performs a secondary enumeration routine by iterating through drive letters A through Z while verifying their existence on disk. This brute-force method ensures broader coverage by identifying volumes that might not be retrieved through WMI queries to maximize visibility into all potential encryption targets.

Directory exclusion list

To maintain system stability and avoid disrupting critical operating system components, the malware excludes a predefined set of directories from traversal and encryption. These directories include core Windows system paths, application directories, and locations commonly associated with security and system management:

Extension exclusion list

The ransomware also excludes a set of file extensions associated with system-critical binaries, configuration files, and executable content:

By avoiding executable files, libraries, scripts, and other system-relevant formats, the malware preserves the integrity of the operating environment. This selective encryption model is a common ransomware design pattern, ensuring that the system remains operational enough for the victim to receive instructions and facilitate ransom payment.

File name exclusion list

The specific file names below are also excluded:

The inclusion of README-GENTLEMEN.txt, the ransomware’s ransom note, prevents it from being encrypted during execution. This ensures that the ransom instructions remain accessible to the victim, which is critical for the operator’s monetization workflow.

Ransom note

During directory traversal, the malware drops a ransom note named README-GENTLEMEN.txt in each scanned directory to provide victim-facing instructions.

The note contains identifiers assigned to the victim, communication channels, and guidance on how to initiate contact with the operators.

File encryption

File ownership

Before encrypting a file, the ransomware modifies the file ownership and access control settings to ensure it has unrestricted write access to the target. This is achieved through the following sequence of commands:

The takeown command recursively transfers ownership of the specified file or directory to the executing user, overriding existing ownership constraints. The icacls command then grants full control permissions to the Everyone security identifier (SID S-1-1-0), applying inheritance flags to propagate these permissions to all child objects. Finally, the attrib command removes the read-only attributes.

Cryptographic scheme

The Gentlemen ransomware implements a hybrid cryptographic design that combines Curve25519 elliptic-curve cryptography with the XChaCha20 stream cipher to achieve efficient and secure per-file encryption.

For each file, the malware performs the following sequence of operations:

1. Generates a unique ephemeral Curve25519 key pair, consisting of a randomly generated private key and its corresponding public key
2. Computes the Elliptic-curve Diffie–Hellman (ECDH) shared secret between the ephemeral private key and the operator’s embedded public key
3. Uses the resulting shared secret as the XChaCha20 key, and derives the nonce from the first 24 bytes of the ephemeral public key
4. Encrypts the file contents using XChaCha20 with this key and nonce combination
5. Appends the Base64-encoded ephemeral public key to the file footer to enable subsequent key reconstruction during decryption

In this sample, the operator’s public key is hard-coded within the binary as a Base64-encoded value:

This design ensures that each file is encrypted with a distinct key and nonce derived from a per-file ephemeral key exchange, eliminating any possibility of key or nonce reuse across files.

During decryption, the decryptor can use the operator’s Curve25519 private key together with the stored ephemeral public key to reconstruct the ECDH shared secret and recover the XChaCha20 key. The nonce is deterministically reconstructed by extracting the first 24 bytes of the recovered ephemeral public key, making separate nonce storage unnecessary.

Overall, this approach provides strong cryptographic isolation between encrypted files while maintaining operational simplicity and efficiency for the threat actor during both encryption and decryption.

Size-based encryption

The malware uses different encryption strategies based on file size:

Small files that are less than 1MB in size are fully encrypted. This ensures that documents, configuration files, and other small but critical data are completely corrupted. For larger files such as databases, virtual disk images, archives, full encryption would be time-consuming. Instead, the malware encrypts three data chunks distributed across the file, which is sufficient to corrupt the file structure while dramatically reducing encryption time.

After encryption, each affected file is renamed with the appended extension .umc16h. This extension serves as a quick indicator of files already encrypted by the ransomware.

Large file chunking logic

For files larger than 1 MB, the malware performs partial encryption by dividing the file into three non-contiguous chunks distributed across its contents:

The first chunk begins at the start of the file, the second is positioned near the midpoint, and the third is located toward the end. This distribution ensures that even limited encryption is sufficient to corrupt the file structure while minimizing processing time.

Each chunk is encrypted in 64 KB (0x10000) blocks using XChaCha20. To maintain cryptographic separation between chunks, the malware modifies the nonce on a per-chunk basis. Specifically, the last byte of the 24-byte XChaCha20 nonce is XOR-ed with the chunk index (0, 1, or 2), and a new cipher instance is initialized for each chunk using the modified nonce. As a result, chunk 0 uses the original nonce, while subsequent chunks use deterministically altered variants.

Although all chunks for a given file share the same derived encryption key, this nonce mutation ensures that each chunk is processed under a unique keystream, preventing keystream reuse across different regions of the file.

The encryption percentage for each file is determined by the provided speed command-line arguments:

File footer

After encrypting each file, the malware appends a structured footer containing metadata required for identification and decryption. The footer format differs slightly depending on whether the file was fully or partially encrypted.

Small file encryption (files ≤ 1 MB):

Large file encryption (files > 1 MB):

The footer serves three primary functions:

1. Key and nonce reconstruction: The Base64-encoded ephemeral public key, located after --eph--, allows the decryptor to recompute both the XChaCha20 key (using ECDH shared secret) and the nonce (first 24 bytes of the ephemeral public key).
2. Identification: The GENTLEMEN marker, located after --marker--, serves as a unique identifier, allowing encryptors/decryptors to quickly determine that the file has been encrypted by The Gentlemen ransomware.
3. Decryption mode: The optional speed flag marker (only present on large files) tells the decryptor which chunking percentage was used.

Notably, the speed marker is only present for large-file encryption. Files that are ≤ 1 MB do not include a speed marker, and its absence signals that the file was fully encrypted. This implicit encoding in the footer allows the decryptor to distinguish between full and partial encryption modes without requiring additional metadata fields.

Post-encryption

Wallpaper setup

If the --silent argument is not provided, the malware drops the following bitmap image file to %TEMP%\gentlemen.bmp and sets it as the system’s desktop wallpaper.

This behavior serves as an immediate visual indicator of compromise, signaling to the victim that encryption has completed.

Self-propagation

The self-propagation module is the more distinctive component of The Gentlemen ransomware. When enabled with the --spread argument, it turns the malware from a single-host encryptor into a self-propagating worm that attempts to deploy its encryptor to every reachable system on the network.

The --spread argument accepts either explicit credentials in domain/user:password format for authenticated lateral movement, or an empty string to reuse the current session’s authentication token.

Placeholder legend

The executed commands in this section use the following placeholders:

Phase 1: Local staging setup

The malware prepares the infected host to act as a distribution point for its binary by executing the following command sequence:

The commands copy the malware executable into C:\Temp, creates a hidden Server Message Block (SMB) share named share$ pointing to that directory, and modifies registry settings to allow anonymous access. With this setup, other systems on the network can retrieve the payload from \\<self>\share$, even when valid credentials are not available.

Phase 2: PsExec drop

The malware binary carries an embedded copy of PsExec and drops it to C:\Temp\psexec.exe on the infected device.

If the embedded PsExec payload cannot be extracted successfully, the malware falls back to downloading PsExec directly from Microsoft’s Sysinternals Live service using the following PowerShell command:

Phase 3: Network enumeration

After dropping PsExec, the malware attempts to enumerate and discover remote systems on the network, including workstations, servers, and domain controllers. Each discovered host becomes a candidate target for propagation.

Phase 4: PowerShell defense evasion blob

Before attempting to run the payload on a remote system, the malware executes the following PowerShell command on the remote target to weaken local defenses and make payload execution more reliable:

This command disables Microsoft Defender real-time monitoring, adds broad Defender exclusions, turns off Windows Firewall across all profiles, shares local drives, grants permissive New Technology File System (NTFS) access, enables SMB1, and loosens anonymous-access restrictions through Local Security Authority (LSA) registry settings. Together, these changes make the remote system significantly more exposed and ready for the payload deployment step.

Phase 5: Payload deployment

For each discovered remote host, the malware attempts a series of independent lateral movement techniques to execute its payload. Notably, these techniques are executed without dependency on prior success, and each method is attempted regardless of whether earlier attempts fail. This execution model of The Gentlemen’s propagation logic can significantly increase the likelihood that at least one execution path succeeds even in secured environments.

5.1: Remote file copy

The malware first stages its payload on the remote system by copying the encryptor binary over the administrative C$ share:

This operation ensures a local copy of the payload is available on the target host, allowing subsequent execution methods to reference a path that does not depend on network shares.

5.2: PsExec-based execution

If PsExec is successfully dropped or downloaded, the malware leverages it to perform a multi-stage execution sequence on the remote host.

First, the malware executes the PowerShell defense evasion payload to weaken host protections:

After a delay to allow defenses to be disabled, the malware executes the payload from the locally staged path C:\Temp under SYSTEM privileges:

After another sleep period, the malware executes the final command to run the payload with the –h flag for elevated token and –c -f to copy and force execution:

5.3: WMIC process creation

The malware uses WMI via wmic.exe to create remote processes:

The first command executes the defense evasion blob, the second runs the payload from the infected host’s SMB share, and the third runs the pre-staged copy from the target’s local C:\Temp directory.

5.4: Scheduled tasks (user)

The malware creates three scheduled tasks under the target user’s context, each running two minutes after the time when they are created:

The scheduled task DefU is set to run the defense evasion blob, UpdateGU executes the payload from the infected host’s SMB share, and UpdateGU2runs the pre-staged copy from the target’s local C:\Temp directory.

5.5: Scheduled tasks (system)

The same three tasks are repeated, running under the SYSTEM account:

By attempting both user-context and SYSTEM-context task creation, the ransomware can improve its chance of propagation across environments with different permission boundaries.

5.6: Service-based execution

The malware executes the following command sequence to create three Windows services on the target host:

Similar to the scheduled tasks, the service DefSvc is set to run the defense evasion blob, UpdateSvc executes the payload from the infected host’s SMB share, and UpdateSvc2 runs the pre-staged copy from the target’s local C:\Temp directory. These services run as SYSTEM by default, which provides another high-privilege execution path for the ransomware payload on the remote system.

5.7: Payload deployment: PowerShell remoting

Using PowerShell remoting, the malware executes commands directly on the target using Invoke-Command:

This method leverages Windows Remote Management (WinRM), providing an alternative execution channel when PsExec or WMIC are unavailable or blocked.

5.8: PowerShell WMI execution

Finally, the malware uses the PowerShell WMI class interface directly to create remote processes with the following command sequence.

This provides functionality equivalent to wmic.exe, but through a different execution path. As a result, it might succeed in environments where the WMIC binary is restricted but WMI access remains available.

Self-propagation summary

Across all techniques, the malware attempts 21 remote execution operations per target host, spanning multiple APIs, privilege levels, and execution contexts. Each method attempts to launch the payload from:

• The infected host’s SMB share: \\<self>\share$\<payload_name>
• The target host’s locally staged path: C:\Temp\<payload_name>

This redundancy is central to The Gentlemen’s propagation strategy. In secured environments where most lateral movement techniques are mitigated, a single successful execution on a single additional host is sufficient to continue the propagation.

Free space wipe

If the --wipe argument is provided, The Gentlemen ransomware performs an additional post-encryption routine to eliminate recoverable artifacts from disk.

The malware first enumerates all available volume paths on the system. For each volume, it creates a temporary file named wipefile.tmp at the root directory and determines the amount of available free space. It then writes random data to this file in 64 MB blocks until the volume is completely filled. Once the disk space has been exhausted, the temporary file is deleted.

This process effectively overwrites all unallocated disk space with random data, preventing forensic tools from recovering remnants of previously deleted files. This includes cached or temporary versions of original unencrypted data that might still reside on disk. When combined with earlier actions such as Volume Shadow Copy deletion, this behavior reduces the likelihood of data recovery without access to the threat actor’s decryption key.

Self-delete

If the --keep flag is not provided, the malware attempts to remove its executable from disk after completing encryption.

Since a running process cannot directly delete its own binary, the ransomware generates and executes a temporary batch script at <malware_path>.batwith the following contents:

The batch script introduces a short delay by sending three Internet Control Message Protocol (ICMP) echo requests to the local host, pausing execution long enough for the main malware process to terminate. After this delay, the script deletes the original ransomware executable before removing itself. This mechanism helps reduce on-disk artifacts and hinders post-incident forensic analysis by eliminating the ransomware binary from the compromised system.

Defending against The Gentlemen ransomware

Microsoft recommends the following mitigations to reduce the impact of this threat.

• Read the human-operated ransomware threat overview for advice on developing a holistic security posture to prevent ransomware, including credential hygiene and hardening recommendations. 
• Turn on cloud-delivered protection in Microsoft Defender Antivirus or the equivalent for your antivirus product to cover rapidly evolving threat actor tools and techniques. Cloud-based machine learning protections block a huge majority of new and unknown variants. 
• Turn on tamper protection features to prevent threat actors from stopping security services. In addition to tamper protection, you can also enable and configure Microsoft Defender Antivirus always-on protection in Group Policy. 
• Enable controlled folder access. Controlled folder access helps protect your valuable data from malicious apps and threats, such as ransomware. Controlled folder access works by only allowing trusted apps to access protected folders. Protected folders are specified when controlled folder access is configured. Apps that aren’t included in the trusted apps list are prevented from making any changes to files inside protected folders. 
• Run endpoint detection and response (EDR) in block mode so that Microsoft Defender for Endpoint can block malicious artifacts, even when your non-Microsoft antivirus does not detect the threat or when Microsoft Defender Antivirus is running in passive mode. EDR in block mode works behind the scenes to remediate malicious artifacts that are detected post-breach. 
• Configure investigation and remediation in full automated mode to let Microsoft Defender for Endpoint take immediate action on alerts to resolve breaches, significantly reducing alert volume. 
• Configure automatic attack disruption in Microsoft Defender XDR. Automatic attack disruption is designed to contain attacks in progress, limit the impact on an organization’s assets, and provide more time for security teams to remediate the attack fully. 
• Microsoft Defender XDR customers can turn on attack surface reduction rules to prevent several of the infection vectors of this threat. These rules, which can be configured by any user, offer significant hardening against targeted attacks. In observed attacks, Microsoft customers who had the following rules turned on could mitigate the attack in the initial stages and prevent hands-on-keyboard activity:  
  • Block executable files from running unless they meet a prevalence, age, or trusted list criterion 
  • Block process creations originating from PSExec and WMI commands if you’re managing your devices with Intune or another MDM solution. This rule is incompatible with management through Microsoft Endpoint Configuration Manager. 
  • Use advanced protection against ransomware

Microsoft Defender detections and hunting guidance

Microsoft Defender customers can refer to the list of applicable detections below. Microsoft Defender coordinates detection, prevention, investigation, and response across endpoints, identities, email, apps to provide integrated protection against attacks like the threat discussed in this blog.

Microsoft Defender Antivirus

Microsoft Defender Antivirus detects threat components as the following malware:

• Ransom:Win64/Gentlemen

Microsoft Defender for Endpoint

The following alerts might indicate threat activity associated with this threat. These alerts, however, can be triggered by unrelated threat activity and are not monitored in the status cards provided with this report.

• Ransomware-linked threat actor detected
• Ransomware behavior detected in the file system
• Possible ransomware activity
• File backups were deleted
• Potential human-operated malicious activity
• Possible data exfiltration
• Suspicious wallpaper change

The following alerts might indicate threat activity associated with The Gentlemen ransomware if Defender for Endpoint is set to block mode.

• ‘Gentlemen’ ransomware was detected
• ‘Gentlemen’ ransomware was prevented

Microsoft Defender for Cloud Apps

The following alert might indicate threat activity associated with this threat. This alert, however, can be triggered by unrelated threat activity and are not monitored in the status cards provided with this report.

• Ransomware activity

Microsoft Security Copilot

Microsoft Security Copilot is embedded in Microsoft Defender and provides security teams with AI-powered capabilities to summarize incidents, analyze files and scripts, summarize identities, use guided responses, and generate device summaries, hunting queries, and incident reports.

Customers can also deploy AI agents, including the following Microsoft Security Copilot agents, to perform security tasks efficiently:

• Threat Intelligence Briefing agent
• Phishing Triage agent
• Threat Hunting agent
• Dynamic Threat Detection agent

Security Copilot is also available as a standalone experience where customers can perform specific security-related tasks, such as incident investigation, user analysis, and vulnerability impact assessment. In addition, Security Copilot offers developer scenarios that allow customers to build, test, publish, and integrate AI agents and plugins to meet unique security needs.

Threat intelligence reports

Microsoft Defender XDR customers can use the following threat analytics reports in the Defender portal (requires license for at least one Defender XDR product) to get the most up-to-date information about the threat actor, malicious activity, and techniques discussed in this blog. These reports provide the intelligence, protection information, and recommended actions to prevent, mitigate, or respond to associated threats found in customer environments.

Microsoft Defender XDR threat analytics

• Tool profile: Gentlemen ransomware
• Threat overview profile: Human-operated ransomware

Microsoft Security Copilot customers can also use the Microsoft Security Copilot integration in Microsoft Defender Threat Intelligence, either in the Security Copilot standalone portal or in the embedded experience in the Microsoft Defender portal to get more information about this threat actor.

Hunting queries

Microsoft Defender XDR

Microsoft Defender XDR customers can run the following advanced hunting queries to find related activity in their networks:

Known The Gentlemen ransomware files

Search for the file hashes associated with The Gentlemen ransomware activity identified in this report. 

let fileHashes = dynamic(["22b38dad7da097ea03aa28d0614164cd25fafeb1383dbc15047e34c8050f6f67"]);
union
(
   DeviceFileEvents
   | where SHA256 in (fileHashes)
   | project Timestamp, DeviceId, DeviceName, FileName, InitiatingProcessFileName, FileHash = SHA256, SourceTable = "DeviceFileEvents"
),
(
   DeviceEvents
   | where SHA256 in (fileHashes)
   | project Timestamp, DeviceId, DeviceName, FileName, InitiatingProcessFileName, FileHash = 
SHA256, SourceTable = "DeviceEvents"
),
(
   DeviceImageLoadEvents
   | where SHA256 in (fileHashes)
   | project Timestamp, DeviceId, DeviceName, FileName, InitiatingProcessFileName, FileHash = SHA256, SourceTable = "DeviceImageLoadEvents"
),
(
   DeviceProcessEvents
   | where SHA256 in (fileHashes)
   | project Timestamp, DeviceId, DeviceName, FileName, InitiatingProcessFileName, FileHash = SHA256, SourceTable = "DeviceProcessEvents"
)
| order by Timestamp desc

Microsoft Sentinel

Microsoft Sentinel customers can use the TI Mapping analytics (a series of analytics all prefixed with ‘TI map’) to automatically match the malicious domain indicators mentioned in this blog post with data in their workspace. If the TI Map analytics are not currently deployed, customers can install the Threat Intelligence solution from the Microsoft Sentinel Content Hub to have the analytics rule deployed in their Sentinel workspace.

Detect web sessions IP and file hash indicators of compromise using Advanced Security Information Model (ASIM)

The following query checks IP addresses, domains, and file hash IOCs across data sources supported by ASIM web session parser:

//IP list - _Im_WebSession
let lookback = 30d;
let ioc_ip_addr = dynamic([]);
let ioc_sha_hashes =dynamic(["22b38dad7da097ea03aa28d0614164cd25fafeb1383dbc15047e34c8050f6f67"]);
_Im_WebSession(starttime=todatetime(ago(lookback)), endtime=now())
| where DstIpAddr in (ioc_ip_addr) or FileSHA256 in (ioc_sha_hashes)
| summarize imWS_mintime=min(TimeGenerated), imWS_maxtime=max(TimeGenerated),
  EventCount=count() by SrcIpAddr, DstIpAddr, Url, Dvc, EventProduct, EventVendor

Detect files hashes indicators of compromise using ASIM

The following query checks IP addresses and file hash IOCs across data sources supported by ASIM file event parser:

// file hash list - imFileEvent
let ioc_sha_hashes = dynamic(["22b38dad7da097ea03aa28d0614164cd25fafeb1383dbc15047e34c8050f6f67"]);
imFileEvent
| where SrcFileSHA256 in (ioc_sha_hashes) or
TargetFileSHA256 in (ioc_sha_hashes)
| extend AccountName = tostring(split(User, @'')[1]), 
  AccountNTDomain = tostring(split(User, @'')[0])
| extend AlgorithmType = "SHA256"

Indicators of compromise

Acknowledgements

• License to Encrypt: The “Gentlemen” Make Their Move. Cybereason (accessed 2026-02-06)
• Unmasking The Gentlemen Ransomware: Tactics, Techniques, and Procedures Revealed. TrendMicro (accessed 2026-02-06)

Learn more

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The post The Gentlemen ransomware: Dissecting a self-propagating Go encryptor appeared first on Microsoft Security Blog.

Ransomware that combines robust encryption with rapid lateral movement significantly increases the risk and impact of an attack. The Gentlemen ransomware is a ransomware-as-a-service (RaaS) threat that is distinguished by its ability to pair its strong per-file encryption with an aggressive self-propagation capability designed to enable broad network compromise. In addition to using per-file ephemeral Curve25519 keys with XChaCha20 stream cipher, The Gentlemen ransomware attempts to spread across an environment using series of simultaneous, distinct lateral movement methods, increasing the likelihood of widespread impact once initial access is achieved.

Microsoft Threat Intelligence tracks the operators behind the ransomware as Storm-2697, a financially motivated threat actor that manages the RaaS platform known as “The Gentlemen” while affiliates carry out attacks. Emerging around mid-2025, The Gentlemen initially started as a closed ransomware group then began offering its RaaS to affiliates in September 2025. More recently, The Gentlemen operators established an official partnership with BreachForums, a popular cybercriminal marketplace, to recruit affiliates including penetration testers and initial access brokers. Given that The Gentlemen is already a widely adopted RaaS platform, this partnership may lead to increased activity as the program becomes accessible to a broader pool of threat actors.

The operators behind the ransomware use double extortion tactics, encrypting data while also exfiltrating sensitive information to pressure victims through the threat of public release if the ransom is not paid. The ransomware is written in Go and obfuscated with Garble to target the Windows environment. Microsoft has observed The Gentlemen ransomware impacting organizations across education, transportation, healthcare, and financial industries in North America, South America, Europe, Africa, and Asia.

In this blog, we present a detailed analysis of the Gentlemen ransomware encryptor, including its execution flow, defense evasion behaviors, encryption design, and lateral movement techniques. This research is intended to provide defenders, incident responders, and the broader security community with a better understanding of how the threat operates, from initial argument parsing and defense evasion, through its file encryption internals, to the full lateral movement that enables it to propagate across the network. We also provide mitigation guidance, Microsoft Defender detections, hunting queries, and indicators of compromise (IOCs) to help organizations defend against this threat and similar ransomware activity.

Pre-encryption

Command-line argument processing

The ransomware operator can control The Gentlemen encryptor through command-line arguments. A password is required for execution, and optional arguments allow the operator to specify encryption scope, speed, lateral movement, and post-encryption behaviors.

The binary accepts the following arguments:

The --full command-line argument appears to be the intended mode of operation for comprehensive file encryption on the infected device. When this argument is provided, the malware spawns two child processes of itself: one appended with the argument --system to encrypt local volumes under a SYSTEM-privileged scheduled task, and one appended with the argument --shares to encrypt network shares. This separation ensures that the malware can reach both local drives (which might require SYSTEM privileges) and mapped network shares (which are only visible in the user’s session).

The speed arguments (--fast, --superfast, --ultrafast) are mutually exclusive and control how much of each large file is encrypted. When no speed flag is specified, the default per-chunk percentage is 9%. These flags only affect files that are larger than 1 MB, and small files are fully encrypted regardless of the speed setting.

Usage prompt

When the encryptor is executed with no command-line argument, the malware prints a branded usage banner to the console.

It first executes the following PowerShell commands to render a console header:

This is followed by a detailed usage prompt provided by the malware author that documents all available flags with descriptions and examples:

It is worth noting that the file size percentages listed in the usage prompt refer to the total file encryption amount. Internally, the malware encrypts three separate chunks, and the per-chunk percentage used in the code is: fast=3%, superfast=1%, ultrafast=0.3%, default=9%.

Password check

Before executing its primary functionality, the malware validates the --password argument against a hardcoded value embedded within the binary. For the sample analyzed in this blog, the expected password is “9VoAvR7G”. If the provided password does not match, the malware outputs bad args and terminates execution.

This password check is a simple operator authentication mechanism, with each build containing a unique embedded password. Its purpose is to restrict execution to authorized operators and reduce the risk of accidental or unauthorized detonation if the binary is recovered or intercepted. However, because this validation relies on a static comparison, it can be easily identified and bypassed through static analysis techniques.

System encryption: Privilege escalation

When the --system argument is provided (either directly or via the --full argument), the malware creates a scheduled task to re-execute itself as SYSTEM. If a delay value is also specified through the --T argument, the scheduled execution time is adjusted accordingly.

To relaunch itself as SYSTEM, it issues the following sequence of commands:

The malware can only perform this task if it’s executed from an account with administrator privilege. It first deletes any existing task named gentlemen_system to avoid conflicts, creates a new one-time task that runs its binary under the SYSTEM account, and finally triggers that task.

This sequence ensures a clean state by first removing any existing task with the same name (gentlemen_system), creating a new scheduled task that executes the ransomware binary with SYSTEM-level privileges before finally triggering its immediate execution.

When running within this scheduled task context, the malware sets the environment variable LOCKER_BACKGROUND=1. This variable functions as an internal execution flag, indicating that the process is operating as a background encryption worker with elevated privileges, rather than as the original operator-invoked instance.

Defense evasion

Before starting file encryption, the malware executes a sequence of commands to disable defensive controls and remove potential forensic artifacts.

Disable Microsoft Defender

The PowerShell commands disable Microsoft Defender real-time monitoring to remove active protection on the infected device. The malware then adds its own executable to the Defender exclusion list to avoid detection. Finally, it excludes the entire C:\ volume from scanning, reducing the likelihood of subsequent detection during file encryption.

Delete shadow copies and event logs

To further impede recovery efforts, the malware deletes all Volume Shadow Copies using both vssadmin and wmic (Windows Management Instrumentation command-line utility). It then clears the System, Application, and Security event logs using wevtutil to remove key audit trails.

Delete forensics artifacts

These commands remove a variety of forensic artifacts, including prefetch files that track program execution, Defender diagnostic and support logs, and Remote Desktop Protocol (RDP) logs.

Additionally, the malware manually deletes PowerShell command history across all user profiles by removing the following file:

This action eliminates evidence of previously executed PowerShell commands, further reducing the visibility of execution history and threat actor activity.

Process and service termination

Process termination

The malware stops a list of running processes using the command:

The table below summarizes the different categories and processes being targeted:

Service termination

In addition to terminating processes, the malware disables and stops a list of Windows services using the commands:

The table below summarizes the different categories and services being targeted:

Terminating these processes and services serves two primary objectives:

• File access and encryption reliability: Many targeted processes/services, such as databases, Office applications, and backup agents, maintain active file locks. By forcibly terminating these processes, the ransomware ensures that locked files become accessible for encryption.
• Defense and recovery disruption: By stopping backup services, endpoint protection agents, and remote access tools, the malware reduces the likelihood of real-time detection and data restoration from backups.

Collectively, these behaviors maximize encryption coverage while hindering the environment’s ability to detect, respond to, or recover from the attack.

Persistence

The encryptor can establish persistence for itself through two mechanisms: scheduled tasks and registry keys.

Scheduled tasks persistence

For establishing persistence with scheduled tasks, the malware executes the following sequence of commands:

These commands first remove any pre-existing tasks with the same names, then create two persistence mechanisms that execute automatically at system startup. The UpdateSystem task launches the payload in the SYSTEM security context, while the UpdateUser task launches it in the currently signed-in user’s context. This design increases the likelihood that the ransomware will run after reboot regardless of privilege level or sign-in state.

Registry keys persistence

For establishing persistence with the registry, the malware executes the following sequence of commands:

The GupdateS value under HKEY_LOCAL_MACHINE (HKLM) provides device-wide persistence that allows the malware to run at startup for all users, while the GupdateU value under HKEY_CURRENT_USER (HKCU) provides user-scoped persistence within the current profile. By writing to both registry hives, the malware establishes redundant autorun paths across both system-level and user-level execution contexts.

Together, the scheduled tasks and Run key modifications create layered persistence, ensuring that the encryptor is re-executed after a reboot in both privileged and user-context scenarios.

Network share traversal

When the command-line argument --shares is provided, the malware initiates network share discovery and enumeration. It begins by probing all drive letters A through Z to identify mapped network drives using the following commands:

This sequence discovers any drives that are already mapped in the current user’s session, which are then added to the encryption target list.

To further enhance visibility into the network environment, the malware enables multiple Windows network discovery services and their associated firewall rules using the following commands:

The services enabled as part of this process include:

• Function Discovery Resource Publication (fdrespub): Publishes the host’s resources to the network, allowing other systems to detect it.
• Function Discovery Provider Host (fdPHost): Hosts provider components responsible for discovering network resources.
• Simple Service Discovery Protocol (SSDP) Discovery (SSDPSRV): Enables discovery of Universal Plug and Play (UPnP) devices.
• UPnP Device Host (upnphost): Supports the hosting and management of UPnP devices.

Finally, the malware reinforces this configuration by enabling the Network Discovery firewall rule group. This redundancy ensures that firewall restrictions do not limit its network visibility, further maximizing the number of reachable targets for encryption and propagation.

Volume and directory traversal

To enumerate all available volumes on the system, the malware executes the following PowerShell command sequence:

This command queries Windows Management Instrumentation (WMI) for all mounted volumes with drive letter paths and attempts to enumerate Cluster Shared Volumes (CSVs).

Additionally, the malware performs a secondary enumeration routine by iterating through drive letters A through Z while verifying their existence on disk. This brute-force method ensures broader coverage by identifying volumes that might not be retrieved through WMI queries to maximize visibility into all potential encryption targets.

Directory exclusion list

To maintain system stability and avoid disrupting critical operating system components, the malware excludes a predefined set of directories from traversal and encryption. These directories include core Windows system paths, application directories, and locations commonly associated with security and system management:

Extension exclusion list

The ransomware also excludes a set of file extensions associated with system-critical binaries, configuration files, and executable content:

By avoiding executable files, libraries, scripts, and other system-relevant formats, the malware preserves the integrity of the operating environment. This selective encryption model is a common ransomware design pattern, ensuring that the system remains operational enough for the victim to receive instructions and facilitate ransom payment.

File name exclusion list

The specific file names below are also excluded:

The inclusion of README-GENTLEMEN.txt, the ransomware’s ransom note, prevents it from being encrypted during execution. This ensures that the ransom instructions remain accessible to the victim, which is critical for the operator’s monetization workflow.

Ransom note

During directory traversal, the malware drops a ransom note named README-GENTLEMEN.txt in each scanned directory to provide victim-facing instructions.

The note contains identifiers assigned to the victim, communication channels, and guidance on how to initiate contact with the operators.

File encryption

File ownership

Before encrypting a file, the ransomware modifies the file ownership and access control settings to ensure it has unrestricted write access to the target. This is achieved through the following sequence of commands:

The takeown command recursively transfers ownership of the specified file or directory to the executing user, overriding existing ownership constraints. The icacls command then grants full control permissions to the Everyone security identifier (SID S-1-1-0), applying inheritance flags to propagate these permissions to all child objects. Finally, the attrib command removes the read-only attributes.

Cryptographic scheme

The Gentlemen ransomware implements a hybrid cryptographic design that combines Curve25519 elliptic-curve cryptography with the XChaCha20 stream cipher to achieve efficient and secure per-file encryption.

For each file, the malware performs the following sequence of operations:

1. Generates a unique ephemeral Curve25519 key pair, consisting of a randomly generated private key and its corresponding public key
2. Computes the Elliptic-curve Diffie–Hellman (ECDH) shared secret between the ephemeral private key and the operator’s embedded public key
3. Uses the resulting shared secret as the XChaCha20 key, and derives the nonce from the first 24 bytes of the ephemeral public key
4. Encrypts the file contents using XChaCha20 with this key and nonce combination
5. Appends the Base64-encoded ephemeral public key to the file footer to enable subsequent key reconstruction during decryption

In this sample, the operator’s public key is hard-coded within the binary as a Base64-encoded value:

This design ensures that each file is encrypted with a distinct key and nonce derived from a per-file ephemeral key exchange, eliminating any possibility of key or nonce reuse across files.

During decryption, the decryptor can use the operator’s Curve25519 private key together with the stored ephemeral public key to reconstruct the ECDH shared secret and recover the XChaCha20 key. The nonce is deterministically reconstructed by extracting the first 24 bytes of the recovered ephemeral public key, making separate nonce storage unnecessary.

Overall, this approach provides strong cryptographic isolation between encrypted files while maintaining operational simplicity and efficiency for the threat actor during both encryption and decryption.

Size-based encryption

The malware uses different encryption strategies based on file size:

Small files that are less than 1MB in size are fully encrypted. This ensures that documents, configuration files, and other small but critical data are completely corrupted. For larger files such as databases, virtual disk images, archives, full encryption would be time-consuming. Instead, the malware encrypts three data chunks distributed across the file, which is sufficient to corrupt the file structure while dramatically reducing encryption time.

After encryption, each affected file is renamed with the appended extension .umc16h. This extension serves as a quick indicator of files already encrypted by the ransomware.

Large file chunking logic

For files larger than 1 MB, the malware performs partial encryption by dividing the file into three non-contiguous chunks distributed across its contents:

The first chunk begins at the start of the file, the second is positioned near the midpoint, and the third is located toward the end. This distribution ensures that even limited encryption is sufficient to corrupt the file structure while minimizing processing time.

Each chunk is encrypted in 64 KB (0x10000) blocks using XChaCha20. To maintain cryptographic separation between chunks, the malware modifies the nonce on a per-chunk basis. Specifically, the last byte of the 24-byte XChaCha20 nonce is XOR-ed with the chunk index (0, 1, or 2), and a new cipher instance is initialized for each chunk using the modified nonce. As a result, chunk 0 uses the original nonce, while subsequent chunks use deterministically altered variants.

Although all chunks for a given file share the same derived encryption key, this nonce mutation ensures that each chunk is processed under a unique keystream, preventing keystream reuse across different regions of the file.

The encryption percentage for each file is determined by the provided speed command-line arguments:

File footer

After encrypting each file, the malware appends a structured footer containing metadata required for identification and decryption. The footer format differs slightly depending on whether the file was fully or partially encrypted.

Small file encryption (files ≤ 1 MB):

Large file encryption (files > 1 MB):

The footer serves three primary functions:

1. Key and nonce reconstruction: The Base64-encoded ephemeral public key, located after --eph--, allows the decryptor to recompute both the XChaCha20 key (using ECDH shared secret) and the nonce (first 24 bytes of the ephemeral public key).
2. Identification: The GENTLEMEN marker, located after --marker--, serves as a unique identifier, allowing encryptors/decryptors to quickly determine that the file has been encrypted by The Gentlemen ransomware.
3. Decryption mode: The optional speed flag marker (only present on large files) tells the decryptor which chunking percentage was used.

Notably, the speed marker is only present for large-file encryption. Files that are ≤ 1 MB do not include a speed marker, and its absence signals that the file was fully encrypted. This implicit encoding in the footer allows the decryptor to distinguish between full and partial encryption modes without requiring additional metadata fields.

Post-encryption

Wallpaper setup

If the --silent argument is not provided, the malware drops the following bitmap image file to %TEMP%\gentlemen.bmp and sets it as the system’s desktop wallpaper.

This behavior serves as an immediate visual indicator of compromise, signaling to the victim that encryption has completed.

Self-propagation

The self-propagation module is the more distinctive component of The Gentlemen ransomware. When enabled with the --spread argument, it turns the malware from a single-host encryptor into a self-propagating worm that attempts to deploy its encryptor to every reachable system on the network.

The --spread argument accepts either explicit credentials in domain/user:password format for authenticated lateral movement, or an empty string to reuse the current session’s authentication token.

Placeholder legend

The executed commands in this section use the following placeholders:

Phase 1: Local staging setup

The malware prepares the infected host to act as a distribution point for its binary by executing the following command sequence:

The commands copy the malware executable into C:\Temp, creates a hidden Server Message Block (SMB) share named share$ pointing to that directory, and modifies registry settings to allow anonymous access. With this setup, other systems on the network can retrieve the payload from \\<self>\share$, even when valid credentials are not available.

Phase 2: PsExec drop

The malware binary carries an embedded copy of PsExec and drops it to C:\Temp\psexec.exe on the infected device.

If the embedded PsExec payload cannot be extracted successfully, the malware falls back to downloading PsExec directly from Microsoft’s Sysinternals Live service using the following PowerShell command:

Phase 3: Network enumeration

After dropping PsExec, the malware attempts to enumerate and discover remote systems on the network, including workstations, servers, and domain controllers. Each discovered host becomes a candidate target for propagation.

Phase 4: PowerShell defense evasion blob

Before attempting to run the payload on a remote system, the malware executes the following PowerShell command on the remote target to weaken local defenses and make payload execution more reliable:

This command disables Microsoft Defender real-time monitoring, adds broad Defender exclusions, turns off Windows Firewall across all profiles, shares local drives, grants permissive New Technology File System (NTFS) access, enables SMB1, and loosens anonymous-access restrictions through Local Security Authority (LSA) registry settings. Together, these changes make the remote system significantly more exposed and ready for the payload deployment step.

Phase 5: Payload deployment

For each discovered remote host, the malware attempts a series of independent lateral movement techniques to execute its payload. Notably, these techniques are executed without dependency on prior success, and each method is attempted regardless of whether earlier attempts fail. This execution model of The Gentlemen’s propagation logic can significantly increase the likelihood that at least one execution path succeeds even in secured environments.

5.1: Remote file copy

The malware first stages its payload on the remote system by copying the encryptor binary over the administrative C$ share:

This operation ensures a local copy of the payload is available on the target host, allowing subsequent execution methods to reference a path that does not depend on network shares.

5.2: PsExec-based execution

If PsExec is successfully dropped or downloaded, the malware leverages it to perform a multi-stage execution sequence on the remote host.

First, the malware executes the PowerShell defense evasion payload to weaken host protections:

After a delay to allow defenses to be disabled, the malware executes the payload from the locally staged path C:\Temp under SYSTEM privileges:

After another sleep period, the malware executes the final command to run the payload with the –h flag for elevated token and –c -f to copy and force execution:

5.3: WMIC process creation

The malware uses WMI via wmic.exe to create remote processes:

The first command executes the defense evasion blob, the second runs the payload from the infected host’s SMB share, and the third runs the pre-staged copy from the target’s local C:\Temp directory.

5.4: Scheduled tasks (user)

The malware creates three scheduled tasks under the target user’s context, each running two minutes after the time when they are created:

The scheduled task DefU is set to run the defense evasion blob, UpdateGU executes the payload from the infected host’s SMB share, and UpdateGU2runs the pre-staged copy from the target’s local C:\Temp directory.

5.5: Scheduled tasks (system)

The same three tasks are repeated, running under the SYSTEM account:

By attempting both user-context and SYSTEM-context task creation, the ransomware can improve its chance of propagation across environments with different permission boundaries.

5.6: Service-based execution

The malware executes the following command sequence to create three Windows services on the target host:

Similar to the scheduled tasks, the service DefSvc is set to run the defense evasion blob, UpdateSvc executes the payload from the infected host’s SMB share, and UpdateSvc2 runs the pre-staged copy from the target’s local C:\Temp directory. These services run as SYSTEM by default, which provides another high-privilege execution path for the ransomware payload on the remote system.

5.7: Payload deployment: PowerShell remoting

Using PowerShell remoting, the malware executes commands directly on the target using Invoke-Command:

This method leverages Windows Remote Management (WinRM), providing an alternative execution channel when PsExec or WMIC are unavailable or blocked.

5.8: PowerShell WMI execution

Finally, the malware uses the PowerShell WMI class interface directly to create remote processes with the following command sequence.

This provides functionality equivalent to wmic.exe, but through a different execution path. As a result, it might succeed in environments where the WMIC binary is restricted but WMI access remains available.

Self-propagation summary

Across all techniques, the malware attempts 21 remote execution operations per target host, spanning multiple APIs, privilege levels, and execution contexts. Each method attempts to launch the payload from:

• The infected host’s SMB share: \\<self>\share$\<payload_name>
• The target host’s locally staged path: C:\Temp\<payload_name>

This redundancy is central to The Gentlemen’s propagation strategy. In secured environments where most lateral movement techniques are mitigated, a single successful execution on a single additional host is sufficient to continue the propagation.

Free space wipe

If the --wipe argument is provided, The Gentlemen ransomware performs an additional post-encryption routine to eliminate recoverable artifacts from disk.

The malware first enumerates all available volume paths on the system. For each volume, it creates a temporary file named wipefile.tmp at the root directory and determines the amount of available free space. It then writes random data to this file in 64 MB blocks until the volume is completely filled. Once the disk space has been exhausted, the temporary file is deleted.

This process effectively overwrites all unallocated disk space with random data, preventing forensic tools from recovering remnants of previously deleted files. This includes cached or temporary versions of original unencrypted data that might still reside on disk. When combined with earlier actions such as Volume Shadow Copy deletion, this behavior reduces the likelihood of data recovery without access to the threat actor’s decryption key.

Self-delete

If the --keep flag is not provided, the malware attempts to remove its executable from disk after completing encryption.

Since a running process cannot directly delete its own binary, the ransomware generates and executes a temporary batch script at <malware_path>.batwith the following contents:

The batch script introduces a short delay by sending three Internet Control Message Protocol (ICMP) echo requests to the local host, pausing execution long enough for the main malware process to terminate. After this delay, the script deletes the original ransomware executable before removing itself. This mechanism helps reduce on-disk artifacts and hinders post-incident forensic analysis by eliminating the ransomware binary from the compromised system.

Defending against The Gentlemen ransomware

Microsoft recommends the following mitigations to reduce the impact of this threat.

• Read the human-operated ransomware threat overview for advice on developing a holistic security posture to prevent ransomware, including credential hygiene and hardening recommendations. 
• Turn on cloud-delivered protection in Microsoft Defender Antivirus or the equivalent for your antivirus product to cover rapidly evolving threat actor tools and techniques. Cloud-based machine learning protections block a huge majority of new and unknown variants. 
• Turn on tamper protection features to prevent threat actors from stopping security services. In addition to tamper protection, you can also enable and configure Microsoft Defender Antivirus always-on protection in Group Policy. 
• Enable controlled folder access. Controlled folder access helps protect your valuable data from malicious apps and threats, such as ransomware. Controlled folder access works by only allowing trusted apps to access protected folders. Protected folders are specified when controlled folder access is configured. Apps that aren’t included in the trusted apps list are prevented from making any changes to files inside protected folders. 
• Run endpoint detection and response (EDR) in block mode so that Microsoft Defender for Endpoint can block malicious artifacts, even when your non-Microsoft antivirus does not detect the threat or when Microsoft Defender Antivirus is running in passive mode. EDR in block mode works behind the scenes to remediate malicious artifacts that are detected post-breach. 
• Configure investigation and remediation in full automated mode to let Microsoft Defender for Endpoint take immediate action on alerts to resolve breaches, significantly reducing alert volume. 
• Configure automatic attack disruption in Microsoft Defender XDR. Automatic attack disruption is designed to contain attacks in progress, limit the impact on an organization’s assets, and provide more time for security teams to remediate the attack fully. 
• Microsoft Defender XDR customers can turn on attack surface reduction rules to prevent several of the infection vectors of this threat. These rules, which can be configured by any user, offer significant hardening against targeted attacks. In observed attacks, Microsoft customers who had the following rules turned on could mitigate the attack in the initial stages and prevent hands-on-keyboard activity:  
  • Block executable files from running unless they meet a prevalence, age, or trusted list criterion 
  • Block process creations originating from PSExec and WMI commands if you’re managing your devices with Intune or another MDM solution. This rule is incompatible with management through Microsoft Endpoint Configuration Manager. 
  • Use advanced protection against ransomware

Microsoft Defender detections and hunting guidance

Microsoft Defender customers can refer to the list of applicable detections below. Microsoft Defender coordinates detection, prevention, investigation, and response across endpoints, identities, email, apps to provide integrated protection against attacks like the threat discussed in this blog.

Microsoft Defender Antivirus

Microsoft Defender Antivirus detects threat components as the following malware:

• Ransom:Win64/Gentlemen

Microsoft Defender for Endpoint

The following alerts might indicate threat activity associated with this threat. These alerts, however, can be triggered by unrelated threat activity and are not monitored in the status cards provided with this report.

• Ransomware-linked threat actor detected
• Ransomware behavior detected in the file system
• Possible ransomware activity
• File backups were deleted
• Potential human-operated malicious activity
• Possible data exfiltration
• Suspicious wallpaper change

The following alerts might indicate threat activity associated with The Gentlemen ransomware if Defender for Endpoint is set to block mode.

• ‘Gentlemen’ ransomware was detected
• ‘Gentlemen’ ransomware was prevented

Microsoft Defender for Cloud Apps

The following alert might indicate threat activity associated with this threat. This alert, however, can be triggered by unrelated threat activity and are not monitored in the status cards provided with this report.

• Ransomware activity

Microsoft Security Copilot

Microsoft Security Copilot is embedded in Microsoft Defender and provides security teams with AI-powered capabilities to summarize incidents, analyze files and scripts, summarize identities, use guided responses, and generate device summaries, hunting queries, and incident reports.

Customers can also deploy AI agents, including the following Microsoft Security Copilot agents, to perform security tasks efficiently:

• Threat Intelligence Briefing agent
• Phishing Triage agent
• Threat Hunting agent
• Dynamic Threat Detection agent

Security Copilot is also available as a standalone experience where customers can perform specific security-related tasks, such as incident investigation, user analysis, and vulnerability impact assessment. In addition, Security Copilot offers developer scenarios that allow customers to build, test, publish, and integrate AI agents and plugins to meet unique security needs.

Threat intelligence reports

Microsoft Defender XDR customers can use the following threat analytics reports in the Defender portal (requires license for at least one Defender XDR product) to get the most up-to-date information about the threat actor, malicious activity, and techniques discussed in this blog. These reports provide the intelligence, protection information, and recommended actions to prevent, mitigate, or respond to associated threats found in customer environments.

Microsoft Defender XDR threat analytics

• Tool profile: Gentlemen ransomware
• Threat overview profile: Human-operated ransomware

Microsoft Security Copilot customers can also use the Microsoft Security Copilot integration in Microsoft Defender Threat Intelligence, either in the Security Copilot standalone portal or in the embedded experience in the Microsoft Defender portal to get more information about this threat actor.

Hunting queries

Microsoft Defender XDR

Microsoft Defender XDR customers can run the following advanced hunting queries to find related activity in their networks:

Known The Gentlemen ransomware files

Search for the file hashes associated with The Gentlemen ransomware activity identified in this report. 

let fileHashes = dynamic(["22b38dad7da097ea03aa28d0614164cd25fafeb1383dbc15047e34c8050f6f67"]);
union
(
   DeviceFileEvents
   | where SHA256 in (fileHashes)
   | project Timestamp, DeviceId, DeviceName, FileName, InitiatingProcessFileName, FileHash = SHA256, SourceTable = "DeviceFileEvents"
),
(
   DeviceEvents
   | where SHA256 in (fileHashes)
   | project Timestamp, DeviceId, DeviceName, FileName, InitiatingProcessFileName, FileHash = 
SHA256, SourceTable = "DeviceEvents"
),
(
   DeviceImageLoadEvents
   | where SHA256 in (fileHashes)
   | project Timestamp, DeviceId, DeviceName, FileName, InitiatingProcessFileName, FileHash = SHA256, SourceTable = "DeviceImageLoadEvents"
),
(
   DeviceProcessEvents
   | where SHA256 in (fileHashes)
   | project Timestamp, DeviceId, DeviceName, FileName, InitiatingProcessFileName, FileHash = SHA256, SourceTable = "DeviceProcessEvents"
)
| order by Timestamp desc

Microsoft Sentinel

Microsoft Sentinel customers can use the TI Mapping analytics (a series of analytics all prefixed with ‘TI map’) to automatically match the malicious domain indicators mentioned in this blog post with data in their workspace. If the TI Map analytics are not currently deployed, customers can install the Threat Intelligence solution from the Microsoft Sentinel Content Hub to have the analytics rule deployed in their Sentinel workspace.

Detect web sessions IP and file hash indicators of compromise using Advanced Security Information Model (ASIM)

The following query checks IP addresses, domains, and file hash IOCs across data sources supported by ASIM web session parser:

//IP list - _Im_WebSession
let lookback = 30d;
let ioc_ip_addr = dynamic([]);
let ioc_sha_hashes =dynamic(["22b38dad7da097ea03aa28d0614164cd25fafeb1383dbc15047e34c8050f6f67"]);
_Im_WebSession(starttime=todatetime(ago(lookback)), endtime=now())
| where DstIpAddr in (ioc_ip_addr) or FileSHA256 in (ioc_sha_hashes)
| summarize imWS_mintime=min(TimeGenerated), imWS_maxtime=max(TimeGenerated),
  EventCount=count() by SrcIpAddr, DstIpAddr, Url, Dvc, EventProduct, EventVendor

Detect files hashes indicators of compromise using ASIM

The following query checks IP addresses and file hash IOCs across data sources supported by ASIM file event parser:

// file hash list - imFileEvent
let ioc_sha_hashes = dynamic(["22b38dad7da097ea03aa28d0614164cd25fafeb1383dbc15047e34c8050f6f67"]);
imFileEvent
| where SrcFileSHA256 in (ioc_sha_hashes) or
TargetFileSHA256 in (ioc_sha_hashes)
| extend AccountName = tostring(split(User, @'')[1]), 
  AccountNTDomain = tostring(split(User, @'')[0])
| extend AlgorithmType = "SHA256"

Indicators of compromise

Acknowledgements

• License to Encrypt: The “Gentlemen” Make Their Move. Cybereason (accessed 2026-02-06)
• Unmasking The Gentlemen Ransomware: Tactics, Techniques, and Procedures Revealed. TrendMicro (accessed 2026-02-06)

Learn more

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The post The Gentlemen ransomware: Dissecting a self-propagating Go encryptor appeared first on Microsoft Security Blog.

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Attackers are increasingly abusing Microsoft’s decades-old MSHTA utility to stealthily deliver stealers, loaders, and persistent malware through phishing, fake software downloads, and LOLBIN-based attack chains.

The post Legacy Windows Tool MSHTA Fuels Surge in Silent Malware Attacks appeared first on SecurityWeek.

The researcher dropped the MiniPlasma exploit that uses the original proof-of-concept (PoC) code targeting the bug.

The post Researcher Drops MiniPlasma Windows Exploit for Unpatched 2020 CVE appeared first on SecurityWeek.

In recent years, many sophisticated intrusions have increasingly avoided using noisy exploits, obvious malware, or custom tooling, instead leveraging systems that organizations already trust within their environments. By operating through legitimate and trusted administrative mechanisms, threat actors could more easily blend seamlessly into routine operations and remain undetected.

Microsoft Incident Response investigated an intrusion that followed this pattern. What initially appeared as routine administrative activity was instead found to be a coordinated campaign abusing trusted operational relationships and authentication processes to establish durable access. The threat actor in this incident leveraged a compromised third-party IT services provider and legitimate IT management tools to conduct a stealthy campaign focusing on long-term access, credential theft, and establishing a persistent foothold.

This blog walks through how the intrusion unfolded, why it was difficult to detect, and how trusted systems, including identity infrastructure, operational tooling, and third-party management relationships were leveraged to sustain access. By examining the investigation end to end, we highlight how modern intrusions succeed without reliance on malware-heavy techniques and what defenders can learn from identifying abuse in environments where trust is implicit. We also provide mitigation and protection recommendations, as well as Microsoft Defender detection and hunting guidance to help identify and investigate related activity.

Abuse of trusted relationships as an attack delivery mechanism

Rather than relying on exploits or malware-based delivery, this attack leveraged an existing trusted operational relationship for malicious activity across the environment. The investigation identified HPE Operations Agent (OA), an approved and signed enterprise management tool commonly used for monitoring and administrative automation, as the primary delivery mechanism. Importantly, this did not involve any vulnerability or flaw in HPE OA itself.

Analysis during the incident response process revealed that management of this operational platform had been delegated to a third-party IT services provider, expanding the trust boundary beyond the organization itself. While such arrangements are operationally common, they introduce implicit trust paths that, if compromised, could be leveraged by threat actors to move within the environment using legitimate access and tooling.

By operating through the HPE OA framework, the threat actor executed scripts and binaries in a manner indistinguishable from normal operations, allowing malicious activity to blend seamlessly into expected behavior and delaying detection.

This technique aligns with MITRE ATT&CK T1199 – Trusted Relationship, in which threat actors exploit established trust relationships to extend access. In this case, the threat actor’s ability to operate entirely through trusted systems allowed them to establish a foothold and execute follow-on actions without relying on exploit-driven techniques.

Attack timeline

This timeline provides a high-level summary of the intrusion, highlighting key phases of the attack. A detailed analysis of each stage is presented in the sections that follow.

Day 1: Initial foothold established

The threat actor gained initial access to the environment by compromising a third-party IT services provider and began operating through trusted systems, enabling execution without triggering immediate alerts.

Days 9–14: Credential access achieved

Credential interception capabilities were introduced on domain infrastructure, allowing the threat actor to harvest and reuse credentials to expand access across devices.

Days 24–32: Web-based persistence established

Persistent access was established on internet-facing servers, enabling the threat actor to maintain repeated access even if individual artifacts were removed.

Days 40–60: Lateral movement and remote access

The threat actor leveraged harvested credentials and covert connectivity to move laterally across devices, including highly sensitive assets.

Days 54–55: Additional credential interception deployed

Credential harvesting was further expanded on domain controllers, ensuring continued access during authentication and password change events.

Days 104–106: Persistence reestablished

Following initial detection, the threat actor returned to previously established access points to reenable persistence and deploy additional tooling.

Day 123: Incident response engagement

Microsoft Incident Response was engaged to investigate the intrusion.

Methods, tools, and access strategies

Initial access

During the investigation, two internet-exposed web servers, WEB-01 and WEB-02, were identified as the earliest known compromised assets. A web shell, Errors.aspx, was discovered on both of these devices; however, there was no indication that the servers had been previously exploited, and the mechanism that deployed the web shells couldn’t be determined.

Using intelligence from Microsoft Threat Intelligence regarding a known malicious domain, Microsoft Incident Response was able to identify a workstation communicating with this infrastructure. This led to the discovery of an execution path involving this domain, which revealed another execution path in which VBScripts (abc003.vbs) were deployed through HPE Operations Manager (HPOM).

HPOM and HPE OA form a distributed IT infrastructure monitoring platform. HPOM functions as a centralized management console for monitoring devices’ health, performance, and availability, while HPE OA is deployed on managed hosts to collect telemetry and execute automated, scheduled, or operator-initiated actions across the environment. In this case, the HPOM was operated by a third-party service provider responsible for managing the customer’s infrastructure.

The threat actor, operating HPOM, executed VBScripts on multiple servers, including the web server and a domain controller. The VBScripts had the following functionality:

• System network configuration discovery
• Active Directory discovery
• External IP address discovery through PowerShell

Credential access

After gaining initial access, the threat actor shifted focus to credential harvesting. The threat actor registered a legitimate network provider named mslogon on the domain controller DC01 through the same HP OA to hijack the authentication process. Network providers integrate into the Windows authentication mechanism, allowing the threat actor to capture cleartext user credentials during user sign-in and password changes. By delivering the component through a trusted and legitimate management channel, the threat actor was able to blend in with routine administrative activity and remain undetected for an extended period.

Analysis of the deployed network provider dynamic link library (DLL), mslogon.dll, revealed the deliberate abuse of Windows Credential Manager APIs, specifically NPLogonNotify and NPPasswordChangeNotify. These APIs are designed to notify registered providers during authentication events.

NPLogonNotify is triggered when a user performs an interactive sign in. When triggered, the DLL captures the submitted username and password in cleartext.

NPPasswordChangeNotify is invoked when a user changes their password using secure attention sequence (Ctrl+Alt+Delete). When triggered, the DLL captured both the old and new credential pairs. These passwords are stored in cleartext under C:\Users\Public\Music\abc123c.d. This file enabled the threat actors to reuse both the current valid credentials and historical passwords for lateral movement.

Later in the intrusion, on DC01 and DC02, the threat actor registered a malicious password filter, passms.dll, into the Windows authentication process by adding it to the Local Security Authority (LSA) notification packageconfiguration. Password filters are loaded by the Local Security Authority Subsystem Service (LSASS) on domain controllers and are invoked whenever a password is set or changed. This abused a legitimate Windows extensibility mechanism, which helped the threat actor blend in and remain undetected for an extended period; similar tactics were observed earlier in the intrusion.

During a password change operation, LSASS calls the PasswordFilter() API for each DLL listed under the Notification Packages registry value (Figure 5). The function receives the username and password in cleartext as input parameters. By registering a malicious password filter, the threat actor gained visibility into password modification events at the system level, allowing credential capture during normal authentication workflows.

When triggered, passms.dll intercepted the credential data and wrote the output toC:\ProgramData\WindowsUpdateService\UpdateDir\Ipd. The captured data was not stored in cleartext. Instead, it was double encoded, first by using Base64, followed by a custom encoding routine embedded within the DLL.

A second module, msupdate.dll, was created on DC01 and DC02 which operated alongside passms.dll. It was invoked using the following command:

Once invoked, the module read the contents of the Ipd file and transferred the encoded data over Server Message Block (SMB) to remote shares. The data was written into a file named icon02.jpeg, likely intended to blend with legitimate image assets.

In addition to SMB-based staging, msupdate.dll also contained email exfiltration capabilities. The module could send messages with the subject line “Update Service” using a predefined Simple Mail Transfer Protocol (SMTP) server, recipient address, and credentials retrieved from local files.

Execution

Execution was achieved through the abuse of an existing enterprise automation channel, allowing malicious VBScript and PowerShell scripts to run under the context of trusted system processes. By leveraging HPE OA to launch abc003.vbs, the threat actor performed system, network, and Active Directory discovery, while maintaining a low-noise execution profile.

On internet-facing web servers, execution was achieved through web shells (Errors.aspx and modified Signoff.aspx), which were used to run PowerShell scripts, deploy binaries, and trigger follow-on activity such as credential access and tunnelling tools.

Persistence

Web shells were the primary persistence mechanisms deployed on internet-facing web servers, WEB-01 and WEB-02. An initial web shell, Errors.aspx,allowed the threat actor to write files to disk. This was later used to modify a legitimate application page, Signoff.aspx, to load a secondary web shell, ghost.inc, from the Windows temporary directory. The secondary web shell provided command execution, file upload, and download capabilities, enabling repeated access even if individual artifacts were removed. This persistence relied on modifying existing application files rather than introducing new services, reducing the likelihood of detection.

The HPE OA was present on both servers and was highly likely used to deploy the web shell. However, because neither server had endpoint detection and response (EDR) coverage, Microsoft Incident Response was unable to confirm this. As a result, the origin and creation mechanism of the web shell, Errors.aspx, on the web server remain unknown.

Persistence was reinforced through the registration of malicious authentication components on domain controllers, DC01 and DC02, ensuring credential interception continued across reboot and credential reset events.

Prior to establishing persistent access, the threat actor first identified internal servers with outbound internet connectivity that could support tunneling. This discovery led to subsequent deployment of ngrok as a persistence mechanism. Instances of ngrok were launched on these internal servers, exposing them through encrypted tunnels to the threat actor’s infrastructure. These tunnels enabled continued inbound access for Remote Desktop Protocol (RDP) sessions without requiring exposed firewall ports, allowing persistence even in environments with restrictive perimeter controls.

Lateral movement

After establishing credential access, execution, and persistence, the threat actor moved laterally using a combination of valid credentials, remote management protocols, and covert network tunnelling using ngrok.

A compromised high-privileged account was used to initiate RDP sessions across the environment, enabling interactive access to critical devices including SQL servers and domain controllers.

To conceal the true source of these connections, the threat actor deployed ngrok, creating encrypted tunnels that exposed internal devices to the internet while bypassing perimeter-based monitoring. Evidence showed RDP connections originating from the ngrok tunnel hosted on SQL-01, masking the threat actor’s real infrastructure and complicating network-based detection.

Lateral movement was further supported by Windows Management Instrumentation (WMI)-based remote execution, which was used to deploy and launch ngrok on additional devices from compromised web servers.

Compromised credentials harvested using password filter DLLs and malicious network provider DLLs on domain controllers enabled continued access and movement without the need for exploit-based techniques.

Campaign conclusion

This campaign demonstrated sustained operational maturity, reinforcing a consistent pattern: long-term access, commonly used tools, and campaigns designed to achieve strategic impact.

A recurring lesson from this activity is the abuse of trusted relationships. Third-party service providers and integrated management tools can become enforcement gaps when visibility is limited or validation is assumed. Threat actors understand this. They leverage legitimate components, trusted update paths, and approved integrations to anchor themselves inside environments that appear compliant on the surface.

Defenders should adopt a posture of deliberate verification. Trust your vendors and tooling but validate their behavior within your environment. Organizations operating in sensitive sectors should assume that threat actors with this level of tradecraft will continue refining third party abuse, credential interception, and stealthy persistence mechanisms to maintain strategic access.

Mitigation and protection guidance

Microsoft recommends the following mitigation measures to defend against such stealthy campaigns described in this blog.

• Turn on cloud-delivered protection in Microsoft Defender Antivirus or the equivalent for your antivirus product to cover rapidly evolving attacker tools and techniques. Cloud-based machine learning protections block a majority of new and unknown variants.
• Deploy endpoint detection and response (EDR) across all endpoints to strengthen visibility, accelerate detection, and improve response to malicious activity.
• Adopt a default-deny egress filtering model so servers only allow explicitly approved outbound traffic, reducing opportunities for communication with malicious command-and-control and data exfiltration.
• Remove unnecessary software and tools from systems to reduce the attack surface and limit opportunities for attacker abuse.
• Enable detailed logging and monitoring on web servers and actively watch for anomalies (such as unexpected file changes or suspicious web requests).
• Implement the enterprise access model to contain privilege escalation and enforce stronger access controls across the environment.
• Strengthen security operations center (SOC) monitoring and incident response by addressing detection, response, and operational gaps identified during the incident.

Microsoft Defender detection and hunting guidance

Microsoft Defender customers can refer to the list of applicable detections below. Microsoft Defender XDR coordinates detection, prevention, investigation, and response across endpoints, identities, email, apps to provide integrated protection against attacks like the threat discussed in this blog.

Microsoft Security Copilot

Microsoft Security Copilot is embedded in Microsoft Defender and provides security teams with AI-powered capabilities to summarize incidents, analyze files and scripts, summarize identities, use guided responses, and generate device summaries, hunting queries, and incident reports.

Customers can also deploy AI agents, including the following Microsoft Security Copilot agents, to perform security tasks efficiently:

• Threat Intelligence Briefing agent
• Phishing Triage agent
• Threat Hunting agent
• Dynamic Threat Detection agent

Security Copilot is also available as a standalone experience where customers can perform specific security-related tasks, such as incident investigation, user analysis, and vulnerability impact assessment. In addition, Security Copilot offers developer scenarios that allow customers to build, test, publish, and integrate AI agents and plugins to meet unique security needs.

Hunting queries

Microsoft Defender XDR customers can run the following advanced hunting queries to find related activity in their networks:

Password filters DLL

Look for unsigned / unverified DLLs configured as LSA notification packages.

DeviceRegistryEvents
| where RegistryKey has @"control\LSA"  and RegistryValueName has "Notification Packages" // Filter to LSA registry path
| project DeviceName, RegistryKey, RegistryValueName, RegistryValueData
| extend NotificationPackage = split(RegistryValueData, " ")
| mv-expand NotificationPackage
| extend NotificationPackage = tostring(NotificationPackage)
| extend Path = tolower(strcat(@"c:\windows\system32\", NotificationPackage, ".dll")) // Construct full DLL path in lower-case
| join kind=leftouter (
    DeviceFileEvents
    | extend Path = tolower(strcat(FolderPath)
    | project DeviceName, SHA1, Path
) on DeviceName, Path
| invoke FileProfile(SHA1) // Retrieve file signing information
| where SignatureState in~ ("SignedInvalid", "Unsigned") // Filter for files that are unsigned or have invalid signature
| project-away DeviceName1, SHA11
| distinct *

Network provider DLL

Look for custom network provider DLLs that are not signed and configured for Windows sign in.

let NetworkProviders = DeviceRegistryEvents
| where RegistryKey has @'\Control\NetworkProvider\Order' and RegistryValueName has 'ProviderOrder' // Filtering on 'ProviderOrder' entries
| extend Providers = split(RegistryValueData, ',')
| mv-expand Providers
| extend Providers = trim(@' ', tostring(Providers)) // Trim spaces around each provider name
| where Providers !in~ ('RDPNP','LanmanWorkstation') // Excluding default provider names
| distinct Providers; // Collect unique suspicious provider names
DeviceRegistryEvents
| where RegistryKey has_all (@'\Services\', @'\NetworkProvider') // Only registry keys under a service's NetworkProvider
and RegistryKey has_any (NetworkProviders) and 
RegistryValueName =~ 'ProviderPath'
| project DeviceName, RegistryKey, RegistryValueName, RegistryValueData
| extend Path = tolower(replace_string(RegistryValueData, '%SystemRoot%', @'C:\Windows')) // Normalize path: replace environment variable and use lower-case
| join kind=leftouter (
    DeviceFileEvents
    | extend Path = tolower(strcat(FolderPath))
    | project DeviceName, SHA1, Path
) on DeviceName, Path
| invoke FileProfile(SHA1,1000)
| where SignatureState in~ ("SignedInvalid", "Unsigned")
| distinct *

Learn more

For the latest security research from the Microsoft Threat Intelligence community, check out the Microsoft Threat Intelligence Blog.

To get notified about new publications and to join discussions on social media, follow us on LinkedIn, X (formerly Twitter), and Bluesky.

To hear stories and insights from the Microsoft Threat Intelligence community about the ever-evolving threat landscape, listen to the Microsoft Threat Intelligence podcast.

The post Undermining the trust boundary: Investigating a stealthy intrusion through third-party compromise appeared first on Microsoft Security Blog.

YellowKey is a BitLocker bypass that requires physical access. GreenPlasma enables elevation of privileges to System.

The post Researcher Drops YellowKey, GreenPlasma Windows Zero-Days appeared first on SecurityWeek.

In recent years, many sophisticated intrusions have increasingly avoided using noisy exploits, obvious malware, or custom tooling, instead leveraging systems that organizations already trust within their environments. By operating through legitimate and trusted administrative mechanisms, threat actors could more easily blend seamlessly into routine operations and remain undetected.

Microsoft Incident Response investigated an intrusion that followed this pattern. What initially appeared as routine administrative activity was instead found to be a coordinated campaign abusing trusted operational relationships and authentication processes to establish durable access. The threat actor in this incident leveraged a compromised third-party IT services provider and legitimate IT management tools to conduct a stealthy campaign focusing on long-term access, credential theft, and establishing a persistent foothold.

This blog walks through how the intrusion unfolded, why it was difficult to detect, and how trusted systems, including identity infrastructure, operational tooling, and third-party management relationships were leveraged to sustain access. By examining the investigation end to end, we highlight how modern intrusions succeed without reliance on malware-heavy techniques and what defenders can learn from identifying abuse in environments where trust is implicit. We also provide mitigation and protection recommendations, as well as Microsoft Defender detection and hunting guidance to help identify and investigate related activity.

Abuse of trusted relationships as an attack delivery mechanism

Rather than relying on exploits or malware-based delivery, this attack leveraged an existing trusted operational relationship for malicious activity across the environment. The investigation identified HPE Operations Agent (OA), an approved and signed enterprise management tool commonly used for monitoring and administrative automation, as the primary delivery mechanism. Importantly, this did not involve any vulnerability or flaw in HPE OA itself.

Analysis during the incident response process revealed that management of this operational platform had been delegated to a third-party IT services provider, expanding the trust boundary beyond the organization itself. While such arrangements are operationally common, they introduce implicit trust paths that, if compromised, could be leveraged by threat actors to move within the environment using legitimate access and tooling.

By operating through the HPE OA framework, the threat actor executed scripts and binaries in a manner indistinguishable from normal operations, allowing malicious activity to blend seamlessly into expected behavior and delaying detection.

This technique aligns with MITRE ATT&CK T1199 – Trusted Relationship, in which threat actors exploit established trust relationships to extend access. In this case, the threat actor’s ability to operate entirely through trusted systems allowed them to establish a foothold and execute follow-on actions without relying on exploit-driven techniques.

Attack timeline

This timeline provides a high-level summary of the intrusion, highlighting key phases of the attack. A detailed analysis of each stage is presented in the sections that follow.

Day 1: Initial foothold established

The threat actor gained initial access to the environment by compromising a third-party IT services provider and began operating through trusted systems, enabling execution without triggering immediate alerts.

Days 9–14: Credential access achieved

Credential interception capabilities were introduced on domain infrastructure, allowing the threat actor to harvest and reuse credentials to expand access across devices.

Days 24–32: Web-based persistence established

Persistent access was established on internet-facing servers, enabling the threat actor to maintain repeated access even if individual artifacts were removed.

Days 40–60: Lateral movement and remote access

The threat actor leveraged harvested credentials and covert connectivity to move laterally across devices, including highly sensitive assets.

Days 54–55: Additional credential interception deployed

Credential harvesting was further expanded on domain controllers, ensuring continued access during authentication and password change events.

Days 104–106: Persistence reestablished

Following initial detection, the threat actor returned to previously established access points to reenable persistence and deploy additional tooling.

Day 123: Incident response engagement

Microsoft Incident Response was engaged to investigate the intrusion.

Methods, tools, and access strategies

Initial access

During the investigation, two internet-exposed web servers, WEB-01 and WEB-02, were identified as the earliest known compromised assets. A web shell, Errors.aspx, was discovered on both of these devices; however, there was no indication that the servers had been previously exploited, and the mechanism that deployed the web shells couldn’t be determined.

Using intelligence from Microsoft Threat Intelligence regarding a known malicious domain, Microsoft Incident Response was able to identify a workstation communicating with this infrastructure. This led to the discovery of an execution path involving this domain, which revealed another execution path in which VBScripts (abc003.vbs) were deployed through HPE Operations Manager (HPOM).

HPOM and HPE OA form a distributed IT infrastructure monitoring platform. HPOM functions as a centralized management console for monitoring devices’ health, performance, and availability, while HPE OA is deployed on managed hosts to collect telemetry and execute automated, scheduled, or operator-initiated actions across the environment. In this case, the HPOM was operated by a third-party service provider responsible for managing the customer’s infrastructure.

The threat actor, operating HPOM, executed VBScripts on multiple servers, including the web server and a domain controller. The VBScripts had the following functionality:

• System network configuration discovery
• Active Directory discovery
• External IP address discovery through PowerShell

Credential access

After gaining initial access, the threat actor shifted focus to credential harvesting. The threat actor registered a legitimate network provider named mslogon on the domain controller DC01 through the same HP OA to hijack the authentication process. Network providers integrate into the Windows authentication mechanism, allowing the threat actor to capture cleartext user credentials during user sign-in and password changes. By delivering the component through a trusted and legitimate management channel, the threat actor was able to blend in with routine administrative activity and remain undetected for an extended period.

Analysis of the deployed network provider dynamic link library (DLL), mslogon.dll, revealed the deliberate abuse of Windows Credential Manager APIs, specifically NPLogonNotify and NPPasswordChangeNotify. These APIs are designed to notify registered providers during authentication events.

NPLogonNotify is triggered when a user performs an interactive sign in. When triggered, the DLL captures the submitted username and password in cleartext.

NPPasswordChangeNotify is invoked when a user changes their password using secure attention sequence (Ctrl+Alt+Delete). When triggered, the DLL captured both the old and new credential pairs. These passwords are stored in cleartext under C:\Users\Public\Music\abc123c.d. This file enabled the threat actors to reuse both the current valid credentials and historical passwords for lateral movement.

Later in the intrusion, on DC01 and DC02, the threat actor registered a malicious password filter, passms.dll, into the Windows authentication process by adding it to the Local Security Authority (LSA) notification packageconfiguration. Password filters are loaded by the Local Security Authority Subsystem Service (LSASS) on domain controllers and are invoked whenever a password is set or changed. This abused a legitimate Windows extensibility mechanism, which helped the threat actor blend in and remain undetected for an extended period; similar tactics were observed earlier in the intrusion.

During a password change operation, LSASS calls the PasswordFilter() API for each DLL listed under the Notification Packages registry value (Figure 5). The function receives the username and password in cleartext as input parameters. By registering a malicious password filter, the threat actor gained visibility into password modification events at the system level, allowing credential capture during normal authentication workflows.

When triggered, passms.dll intercepted the credential data and wrote the output toC:\ProgramData\WindowsUpdateService\UpdateDir\Ipd. The captured data was not stored in cleartext. Instead, it was double encoded, first by using Base64, followed by a custom encoding routine embedded within the DLL.

A second module, msupdate.dll, was created on DC01 and DC02 which operated alongside passms.dll. It was invoked using the following command:

Once invoked, the module read the contents of the Ipd file and transferred the encoded data over Server Message Block (SMB) to remote shares. The data was written into a file named icon02.jpeg, likely intended to blend with legitimate image assets.

In addition to SMB-based staging, msupdate.dll also contained email exfiltration capabilities. The module could send messages with the subject line “Update Service” using a predefined Simple Mail Transfer Protocol (SMTP) server, recipient address, and credentials retrieved from local files.

Execution

Execution was achieved through the abuse of an existing enterprise automation channel, allowing malicious VBScript and PowerShell scripts to run under the context of trusted system processes. By leveraging HPE OA to launch abc003.vbs, the threat actor performed system, network, and Active Directory discovery, while maintaining a low-noise execution profile.

On internet-facing web servers, execution was achieved through web shells (Errors.aspx and modified Signoff.aspx), which were used to run PowerShell scripts, deploy binaries, and trigger follow-on activity such as credential access and tunnelling tools.

Persistence

Web shells were the primary persistence mechanisms deployed on internet-facing web servers, WEB-01 and WEB-02. An initial web shell, Errors.aspx,allowed the threat actor to write files to disk. This was later used to modify a legitimate application page, Signoff.aspx, to load a secondary web shell, ghost.inc, from the Windows temporary directory. The secondary web shell provided command execution, file upload, and download capabilities, enabling repeated access even if individual artifacts were removed. This persistence relied on modifying existing application files rather than introducing new services, reducing the likelihood of detection.

The HPE OA was present on both servers and was highly likely used to deploy the web shell. However, because neither server had endpoint detection and response (EDR) coverage, Microsoft Incident Response was unable to confirm this. As a result, the origin and creation mechanism of the web shell, Errors.aspx, on the web server remain unknown.

Persistence was reinforced through the registration of malicious authentication components on domain controllers, DC01 and DC02, ensuring credential interception continued across reboot and credential reset events.

Prior to establishing persistent access, the threat actor first identified internal servers with outbound internet connectivity that could support tunneling. This discovery led to subsequent deployment of ngrok as a persistence mechanism. Instances of ngrok were launched on these internal servers, exposing them through encrypted tunnels to the threat actor’s infrastructure. These tunnels enabled continued inbound access for Remote Desktop Protocol (RDP) sessions without requiring exposed firewall ports, allowing persistence even in environments with restrictive perimeter controls.

Lateral movement

After establishing credential access, execution, and persistence, the threat actor moved laterally using a combination of valid credentials, remote management protocols, and covert network tunnelling using ngrok.

A compromised high-privileged account was used to initiate RDP sessions across the environment, enabling interactive access to critical devices including SQL servers and domain controllers.

To conceal the true source of these connections, the threat actor deployed ngrok, creating encrypted tunnels that exposed internal devices to the internet while bypassing perimeter-based monitoring. Evidence showed RDP connections originating from the ngrok tunnel hosted on SQL-01, masking the threat actor’s real infrastructure and complicating network-based detection.

Lateral movement was further supported by Windows Management Instrumentation (WMI)-based remote execution, which was used to deploy and launch ngrok on additional devices from compromised web servers.

Compromised credentials harvested using password filter DLLs and malicious network provider DLLs on domain controllers enabled continued access and movement without the need for exploit-based techniques.

Campaign conclusion

This campaign demonstrated sustained operational maturity, reinforcing a consistent pattern: long-term access, commonly used tools, and campaigns designed to achieve strategic impact.

A recurring lesson from this activity is the abuse of trusted relationships. Third-party service providers and integrated management tools can become enforcement gaps when visibility is limited or validation is assumed. Threat actors understand this. They leverage legitimate components, trusted update paths, and approved integrations to anchor themselves inside environments that appear compliant on the surface.

Defenders should adopt a posture of deliberate verification. Trust your vendors and tooling but validate their behavior within your environment. Organizations operating in sensitive sectors should assume that threat actors with this level of tradecraft will continue refining third party abuse, credential interception, and stealthy persistence mechanisms to maintain strategic access.

Mitigation and protection guidance

Microsoft recommends the following mitigation measures to defend against such stealthy campaigns described in this blog.

• Turn on cloud-delivered protection in Microsoft Defender Antivirus or the equivalent for your antivirus product to cover rapidly evolving attacker tools and techniques. Cloud-based machine learning protections block a majority of new and unknown variants.
• Deploy endpoint detection and response (EDR) across all endpoints to strengthen visibility, accelerate detection, and improve response to malicious activity.
• Adopt a default-deny egress filtering model so servers only allow explicitly approved outbound traffic, reducing opportunities for communication with malicious command-and-control and data exfiltration.
• Remove unnecessary software and tools from systems to reduce the attack surface and limit opportunities for attacker abuse.
• Enable detailed logging and monitoring on web servers and actively watch for anomalies (such as unexpected file changes or suspicious web requests).
• Implement the enterprise access model to contain privilege escalation and enforce stronger access controls across the environment.
• Strengthen security operations center (SOC) monitoring and incident response by addressing detection, response, and operational gaps identified during the incident.

Microsoft Defender detection and hunting guidance

Microsoft Defender customers can refer to the list of applicable detections below. Microsoft Defender XDR coordinates detection, prevention, investigation, and response across endpoints, identities, email, apps to provide integrated protection against attacks like the threat discussed in this blog.

Microsoft Security Copilot

Microsoft Security Copilot is embedded in Microsoft Defender and provides security teams with AI-powered capabilities to summarize incidents, analyze files and scripts, summarize identities, use guided responses, and generate device summaries, hunting queries, and incident reports.

Customers can also deploy AI agents, including the following Microsoft Security Copilot agents, to perform security tasks efficiently:

• Threat Intelligence Briefing agent
• Phishing Triage agent
• Threat Hunting agent
• Dynamic Threat Detection agent

Security Copilot is also available as a standalone experience where customers can perform specific security-related tasks, such as incident investigation, user analysis, and vulnerability impact assessment. In addition, Security Copilot offers developer scenarios that allow customers to build, test, publish, and integrate AI agents and plugins to meet unique security needs.

Hunting queries

Microsoft Defender XDR customers can run the following advanced hunting queries to find related activity in their networks:

Password filters DLL

Look for unsigned / unverified DLLs configured as LSA notification packages.

DeviceRegistryEvents
| where RegistryKey has @"control\LSA"  and RegistryValueName has "Notification Packages" // Filter to LSA registry path
| project DeviceName, RegistryKey, RegistryValueName, RegistryValueData
| extend NotificationPackage = split(RegistryValueData, " ")
| mv-expand NotificationPackage
| extend NotificationPackage = tostring(NotificationPackage)
| extend Path = tolower(strcat(@"c:\windows\system32\", NotificationPackage, ".dll")) // Construct full DLL path in lower-case
| join kind=leftouter (
    DeviceFileEvents
    | extend Path = tolower(strcat(FolderPath)
    | project DeviceName, SHA1, Path
) on DeviceName, Path
| invoke FileProfile(SHA1) // Retrieve file signing information
| where SignatureState in~ ("SignedInvalid", "Unsigned") // Filter for files that are unsigned or have invalid signature
| project-away DeviceName1, SHA11
| distinct *

Network provider DLL

Look for custom network provider DLLs that are not signed and configured for Windows sign in.

let NetworkProviders = DeviceRegistryEvents
| where RegistryKey has @'\Control\NetworkProvider\Order' and RegistryValueName has 'ProviderOrder' // Filtering on 'ProviderOrder' entries
| extend Providers = split(RegistryValueData, ',')
| mv-expand Providers
| extend Providers = trim(@' ', tostring(Providers)) // Trim spaces around each provider name
| where Providers !in~ ('RDPNP','LanmanWorkstation') // Excluding default provider names
| distinct Providers; // Collect unique suspicious provider names
DeviceRegistryEvents
| where RegistryKey has_all (@'\Services\', @'\NetworkProvider') // Only registry keys under a service's NetworkProvider
and RegistryKey has_any (NetworkProviders) and 
RegistryValueName =~ 'ProviderPath'
| project DeviceName, RegistryKey, RegistryValueName, RegistryValueData
| extend Path = tolower(replace_string(RegistryValueData, '%SystemRoot%', @'C:\Windows')) // Normalize path: replace environment variable and use lower-case
| join kind=leftouter (
    DeviceFileEvents
    | extend Path = tolower(strcat(FolderPath))
    | project DeviceName, SHA1, Path
) on DeviceName, Path
| invoke FileProfile(SHA1,1000)
| where SignatureState in~ ("SignedInvalid", "Unsigned")
| distinct *

Learn more

For the latest security research from the Microsoft Threat Intelligence community, check out the Microsoft Threat Intelligence Blog.

To get notified about new publications and to join discussions on social media, follow us on LinkedIn, X (formerly Twitter), and Bluesky.

To hear stories and insights from the Microsoft Threat Intelligence community about the ever-evolving threat landscape, listen to the Microsoft Threat Intelligence podcast.

The post Undermining the trust boundary: Investigating a stealthy intrusion through third-party compromise appeared first on Microsoft Security Blog.

Fresh security updates resolve critical flaws in Azure, Windows, Dynamics 365, and the SSO Plugin for Jira & Confluence.

The post Microsoft Patches 137 Vulnerabilities appeared first on SecurityWeek.