Google and an assortment of partners shut down a botnet that an approved Android device manufacturer purposefully deployed across more than 1.3 million TV set-top boxes, the company said Monday. 

Videostrong Technology Co., a China-based Android original equipment and device manufacturer, implanted a backdoor into multiple devices it sold. Those backdoors established XCPE, an expansive botnet that cybercriminals used to conduct ad fraud, steal data and route malicious traffic through residential proxy networks, according to a Google Threat Intelligence Group report.

Google took legal action to shut down the domains and servers Videostrong used to control the botnet. The company also took down command-and-control domains that more than a dozen malware families ran as modules through the XCPE backdoor, claiming it disrupted access to at least 10 million additional compromised devices from various manufacturers.

Videostrong sold Android devices with pre-installed malware for years, slipping by Google’s security tests by loading the malicious code after the device’s first boot. “The XCPE operators constantly evolved its configurations to evade Google’s pre and post-launch detections,” Charley Snyder, head of disruption operations at GTIG, told CyberScoop.

Snyder declined to say when or how Google first became aware of the approved vendor running a botnet on Android-powered devices. 

“We found this malicious software built directly into many different device models and brands over multiple years, supported by dedicated infrastructure and constantly evolving configurations to evade detection and manage their affiliates,” Google researchers wrote in the report. “We believe this campaign wasn’t an isolated rogue insider or a development oversight.”

Google banned Videostrong and any future subsidiaries from building or selling certified Android devices, and said it changed its review process to detect and stop similar activities in the future. Yet, Snyder said the company isn’t sharing specifics on these changes because it doesn’t want to provide threat actors insights that might help them circumvent these additional protections.

Most of the devices comprising the XCPE botnet were Android TV set-top boxes, but researchers also observed infected Android-based telehealth devices, karaoke machines and digital signs. 

“Without users’ knowledge or consent, infected devices were offered as a distribution mechanism for a wide array of criminal actors,” researchers wrote in the report. “This led to a variety of malicious activities being conducted on and through the devices, including ad-fraud, data exfiltration, and routing malicious network traffic through the devices.”

The botnet spanned more than 170 countries, with the largest concentration of infected devices based in Malaysia, Brazil, Iraq, Mexico and Taiwan, according to TrendAI researchers. Nearly 44,000 infected devices were based in the United States between June and October.

Google also partnered with Japan’s National Police Agency, Lumen Technologies, Human Security, Plume and Synthient to study and disrupt the botnet. 

The company said the dismantling of XCPE “seriously impacted over a dozen malicious actors,” yet it warned that the underlying market for backdoors, ad fraud and residential proxy networks are resilient and operating as an interconnected supply chain.

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Volt Typhoon, a China-government backed hacking group that has infiltrated America’s critical infrastructure networks for years, has consistently built and dismantled ephemeral malicious infrastructure to burrow into hundreds of sensitive systems undetected, Lumen Technologies’ Black Lotus Labs said in a Wednesday report.

The covert access operation that researchers call “Silent Train” isn’t a standalone network, but rather a series of compromised small office home office (SOHO) routers, internet of things (IoT) devices and enterprise infrastructure that Volt Typhoon has rapidly rotated through since late 2023. 

The Chinese threat group has used this chain of short-lived compromised infrastructure to exploit additional vulnerabilities, including zero-days, in network edge devices and gain deeper, persistent access into victim networks, researchers said. 

“Individual chains are assembled and dismantled every day, with infrastructure continually refreshed,” Michael Horka, principal information security engineer at Black Lotus Labs, told CyberScoop. “Volt Typhoon demonstrated a repeatable capability to rebuild a new chain with different infrastructure in less than two minutes, making the number of nodes at any one moment effectively close to zero.”

Black Lotus Labs has notified hundreds of victims since it first identified Silent Train activity, including telecom providers, government entities, defense contractors, communication services, universities and IT firms. Other victims spanning critical infrastructure include organizations in the water, energy, transportation, maritime, rail, aviation and emergency services sectors.

“The ephemeral nature of the framework means our observations should not be interpreted as a complete census of Volt Typhoon activity,” said Horka, who also was the lead researcher on the report.

The nation-state group’s investment in operational security and preserving access is remarkable, according to Black Lotus Labs.

“We observed infrastructure assembled in under two minutes, sessions averaging roughly four hours, extensive cleanup, compartmentalization and continued development of new access vectors,” Horka said. “That is considerable effort devoted not even to get into their end targets, but purely to making important operations difficult to discover and trace.”

Volt Typhoon relied more heavily on Silent Train after the FBI and Justice Department disrupted the KV Botnet in early 2024, researchers said. Earlier this year, U.S. and global authorities warned about a widespread shift in Chinese hacking groups’ use of covert networks riding on compromised common devices.

The reach of those efforts is extensive and ongoing. Volt Typhoon has exploited and abused more than 27 device classes in Silent Train operations, including edge devices, enterprise management tools, identity and access management systems, networking infrastructure and other technologies. 

“The diversity matters, but the discipline matters even more,” Horka said. “Specific device types were consistently reserved for particular positions in the chain. It operated less like a collection of randomly compromised devices and more like an organized inventory of capabilities.”

The threat group has successfully compromised devices and technologies from Fortinet, Cisco, ManageEngine, Ivanti, F5, Check Point, Palo Alto Networks, ServiceNow, TP-Link, Netgear and ArcGIS, researchers said. Black Lotus Labs also observed confirmed zero-day campaigns targeting Versa Director, N-Able N-Central, Cisco Catalyst SD-WAN and VeloCloud Orchestrator. 

“The exploitation patterns, victimology, and geographic targeting observed throughout our investigation point to a sustained focus on communications, defense, government, and critical infrastructure environments of enduring strategic value,” Black Lotus Labs researchers wrote in the report. “Through repeated targeting of centralized management platforms and control-plane technologies, Silent Train shows how Volt Typhoon systematically pursues and preserves access to some of the most consequential networks in the United States.”

Silent Train’s ephemerality and operational discipline means it can’t be measured in size. These attributes also make it “fundamentally difficult to disrupt because there isn’t one network to take down,” Horka said. 

“What exists today will be completely different tomorrow,” he added. “You can try to remove individual pieces, but removing the actor’s ability to continuously rebuild them is a much harder problem to solve.”

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Malware that takes technical cues from a poem to assemble a growing botnet by targeting open-source AI services has compromised more than 3,400 servers since April, Lumen Technologies’ Black Lotus Labs said in a report Wednesday. 

The poem, which a threat actor wrote and posted on a GitHub repository, seems innocuous but it’s driving a stealthy piece of malware researchers call PoeLLM. Four specific words extracted from the poem, which have been changed at least a dozen times, are converted into a command-and-control server address through a hard-coded dictionary embedded in the malware — a framework that bolsters PoeLLM’s resiliency.

“The most interesting piece of the poem approach is that the IP address used for C2 communications is invisible outside of the victim’s netflow. In other malware samples, there might be a hard-coded fallback C2 address, or URL which points to an IP address written elsewhere on the internet,” Ryan English, information security engineer at Black Lotus Labs, told CyberScoop.

“To anyone who comes across it, this is simply a poem on GitHub. It has no links, no files to download, no encrypted text that could easily be flagged as malicious, even by advanced models,” he added. “There would be no reason for any security researcher to identify this poem as malicious — or know about the IP address hidden within it — unless they had access to the malware referencing it.”

Researchers first encountered PoeLLM infrastructure in June during an investigation into a maximum-severity defect affecting Ivanti’s secure mobile gateway product, Sentry. That discovery uncovered a sweeping exploit-scanning and cryptocurrency-mining botnet linked to multiple compromised services and tools, including LiteLLM, Ollama, Gotenberg and Gitea.

While “PoeLLM has been extremely successful in compromising multiple AI-related services at scale,” the threat actor’s achievements beyond exploit scanning and cryptomining remain under investigation, English said. 

The malware contains functionality that can allow for remote code execution, potentially allowing a threat actor to abuse AI models on victim servers, along with public-facing services for downstream compromise, he added.

“Through the growth of this botnet, the actor has effectively created a private army of AI-enabled proxies, which will continue to multiply and provide additional vectors for attack, credential theft, token abuse and more,” English said.

The botnet has continued to grow by converting compromised servers into attackers and shifting through C2 infrastructure, leaving fewer traces across the internet.

“If one exploit server gets reported by the security community, the attacker can easily pivot and start proxying attacks through hundreds of other compromised victims,” English said. 

The poem serves as a dynamic lookup table for this infrastructure rotation. When the malware retrieves the updated poem from GitHub, it extracts four specific words based on their positions relative to fixed text anchors within the verse. Each extracted word is then matched against a hard-coded dictionary in the malware, where individual words map to sets of IP addresses. The four numbers combine to form the current C2 server address. This means the threat actor can change the entire poem, and thus the C2 location, without updating the malware itself.

“Many of the C2s used in this campaign were never detected on crowd-sourced security tools, indicating that this layer of obfuscation was very helpful in improving the resilience of a C2,” English said.

For instance, the first stanza of the poem, as it was observed last month, reads: “In the silent hum of driver, the machines begin to speak, each pulse of diode threading light through copper veins. We taught the dark to carry meaning, byte by byte — a language built from lightning, cold and clean.”

The malware extracts four specific words from the poem and matches each to a number in a hard-coded dictionary — for example, “driver” equals 92, “diode” equals 119, “decryption” equals 165, and “string” equals 74, combining to form the C2 address. When the threat actor changes the poem’s keywords, the malware automatically calculates a new C2 address without needing to update itself. This keeps the infrastructure invisible to network monitoring tools unless the malware code is directly analyzed.

Black Lotus Labs said the threat actor behind PoeLLM is likely Italian or speaks Italian. Researchers observed multiple comments in the malware code written in Italian and said the threat actor has relied on Italy-based servers for testing and C2 infrastructure. 

Researchers said they don’t know how many people are involved in the PoeLLM’s operation, and they haven’t observed any connections to other groups or campaigns.

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Botnets powered by residential proxy networks are proliferating, enabling cybercriminals of all types to evade detection by blending in with seemingly legitimate traffic, Lumen Technology’s Black Lotus Labs said in a report Friday.

The global scale of botnets observed by Lumen is currently approaching 60 million victim IP addresses, Chris Formosa, senior lead information security engineer at Black Lotus Labs, told CyberScoop. Roughly 1 in 4 of those compromised IPs are based in the United States, and the true number of infected devices is much greater because there are networks beyond Lumen’s visibility and multiple devices are often unknowingly running a malicious proxy network on the same IP. 

Super-sized botnets are also gaining momentum, according to Lumen, with an average of 10 distinct botnets controlling their own populations of about 1 million active victims daily.

“The only reason these botnets keep getting more and more victims is because there is clearly a market. Aside from criminal activity, who wants access to millions of IPs regularly?” Formosa said. 

That demand for botnets fuels opportunities for growth, reselling, collaboration, and quick rebounds following massive disruptions.

IPIDEA, one of the largest residential proxy networks in operation when its infrastructure was disrupted by coordinated strikes in January, recovered at nearly half-strength within hours and earlier this surpassed its pre-disruption botnet size with a current botnet population of about 10 million IPs, researchers said.

“Their rebuild was eye-opening as they began to rebound from that interdiction,” Ryan English, information security engineer at Black Lotus Labs, told CyberScoop. “Even for how quickly some botnets can rebound, theirs was surprising. We’ve seen them all rebuild, but we haven’t seen anybody do it that fast.”

Meanwhile, botnets are continuously growing, as cybercriminals seek out the cover they provide, more cheap and poorly defended devices hit the market and vendors stop providing security updates for older but still usable products. 

“Your available pool for those proxy hunters grows every year, and it will continue to grow every year,” English said, adding that more than 1 billion devices are currently vulnerable and available to be unknowingly sucked up into botnets.

The challenge for defenders is lopsided, and while disruptions and seizures occur relatively often, botnet operators have formed a global supply chain with pathways that are difficult to break. 

“We have observed multiple residential proxy services collaborating to form what amounts to the largest cooperative network ever seen on the internet,” researchers wrote in the report.

Black Lotus Labs currently tracks more than 30 distinct malicious proxy botnet clusters, and most of those regularly boast more than 100,000 daily victims.

“Our understanding of the various botnets in this space, along with experience in multiple disruptions, leads us to a very important conclusion: taking down a single malicious proxy provider or their botnet in isolation is likely to result in a short-lived solution,” researchers wrote. 

“In recent years, the malicious proxy environment has essentially created the largest collective botnet currently active on the internet, capable of moving millions of IPs within hours to wherever they are needed,” they added. “Until the malicious proxy landscape is properly addressed and regulated on both the private industry and law enforcement sides, this issue will grow and, along with the DDoS botnet landscape, will most likely become a greater problem in the long term.”

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