A hacktivist group with links to Iran’s intelligence agencies is claiming responsibility for a data-wiping attack against Stryker, a global medical technology company based in Michigan. News reports out of Ireland, Stryker’s largest hub outside of the United States, said the company sent home more than 5,000 workers there today. Meanwhile, a voicemail message at Stryker’s main U.S. headquarters says the company is currently experiencing a building emergency.

Based in Kalamazoo, Michigan, Stryker [NYSE:SYK] is a medical and surgical equipment maker that reported $25 billion in global sales last year. In a lengthy statement posted to Telegram, a hacktivist group known as Handala (a.k.a. Handala Hack Team) claimed that Stryker’s offices in 79 countries have been forced to shut down after the group erased data from more than 200,000 systems, servers and mobile devices.

A manifesto posted by the Iran-backed hacktivist group Handala, claiming a mass data-wiping attack against medical technology maker Stryker.

“All the acquired data is now in the hands of the free people of the world, ready to be used for the true advancement of humanity and the exposure of injustice and corruption,” a portion of the Handala statement reads.

The group said the wiper attack was in retaliation for a Feb. 28 missile strike that hit an Iranian school and killed at least 175 people, most of them children. The New York Times reports today that an ongoing military investigation has determined the United States is responsible for the deadly Tomahawk missile strike.

Handala was one of several hacker groups recently profiled by Palo Alto Networks, which links it to Iran’s Ministry of Intelligence and Security (MOIS). Palo Alto says Handala surfaced in late 2023 and is assessed as one of several online personas maintained by Void Manticore, a MOIS-affiliated actor.

Stryker’s website says the company has 56,000 employees in 61 countries. A phone call placed Wednesday morning to the media line at Stryker’s Michigan headquarters sent this author to a voicemail message that stated, “We are currently experiencing a building emergency. Please try your call again later.”

A report Wednesday morning from the Irish Examiner said Stryker staff are now communicating via WhatsApp for any updates on when they can return to work. The story quoted an unnamed employee saying anything connected to the network is down, and that “anyone with Microsoft Outlook on their personal phones had their devices wiped.”

“Multiple sources have said that systems in the Cork headquarters have been ‘shut down’ and that Stryker devices held by employees have been wiped out,” the Examiner reported. “The login pages coming up on these devices have been defaced with the Handala logo.”

Wiper attacks usually involve malicious software designed to overwrite any existing data on infected devices. But a trusted source with knowledge of the attack who spoke on condition of anonymity told KrebsOnSecurity the perpetrators in this case appear to have used a Microsoft service called Microsoft Intune to issue a ‘remote wipe’ command against all connected devices.

Intune is a cloud-based solution built for IT teams to enforce security and data compliance policies, and it provides a single, web-based administrative console to monitor and control devices regardless of location. The Intune connection is supported by this Reddit discussion on the Stryker outage, where several users who claimed to be Stryker employees said they were told to uninstall Intune urgently.

Palo Alto says Handala’s hack-and-leak activity is primarily focused on Israel, with occasional targeting outside that scope when it serves a specific agenda. The security firm said Handala also has taken credit for recent attacks against fuel systems in Jordan and an Israeli energy exploration company.

“Recent observed activities are opportunistic and ‘quick and dirty,’ with a noticeable focus on supply-chain footholds (e.g., IT/service providers) to reach downstream victims, followed by ‘proof’ posts to amplify credibility and intimidate targets,” Palo Alto researchers wrote.

The Handala manifesto posted to Telegram referred to Stryker as a “Zionist-rooted corporation,” which may be a reference to the company’s 2019 acquisition of the Israeli company OrthoSpace.

Stryker is a major supplier of medical devices, and the ongoing attack is already affecting healthcare providers. One healthcare professional at a major university medical system in the United States told KrebsOnSecurity they are currently unable to order surgical supplies that they normally source through Stryker.

“This is a real-world supply chain attack,” the expert said, who asked to remain anonymous because they were not authorized to speak to the press. “Pretty much every hospital in the U.S. that performs surgeries uses their supplies.”

John Riggi, national advisor for the American Hospital Association (AHA), said the AHA is not aware of any supply-chain disruptions as of yet.

“We are aware of reports of the cyber attack against Stryker and are actively exchanging information with the hospital field and the federal government to understand the nature of the threat and assess any impact to hospital operations,” Riggi said in an email. “As of this time, we are not aware of any direct impacts or disruptions to U.S. hospitals as a result of this attack. That may change as hospitals evaluate services, technology and supply chain related to Stryker and if the duration of the attack extends.”

According to a March 11 memo from the state of Maryland’s Institute for Emergency Medical Services Systems, Stryker indicated that some of their computer systems have been impacted by a “global network disruption.” The memo indicates that in response to the attack, a number of hospitals have opted to disconnect from Stryker’s various online services, including LifeNet, which allows paramedics to transmit EKGs to emergency physicians so that heart attack patients can expedite their treatment when they arrive at the hospital.

“As a precaution, some hospitals have temporarily suspended their connection to Stryker systems, including LIFENET, while others have maintained the connection,” wrote Timothy Chizmar, the state’s EMS medical director. “The Maryland Medical Protocols for EMS requires ECG transmission for patients with acute coronary syndrome (or STEMI). However, if you are unable to transmit a 12 Lead ECG to a receiving hospital, you should initiate radio consultation and describe the findings on the ECG.”

This is a developing story. Updates will be noted with a timestamp.

Update, 2:54 p.m. ET: Added comment from Riggi and perspectives on this attack’s potential to turn into a supply-chain problem for the healthcare system.

Update, Mar. 12, 7:59 a.m. ET: Added information about the outage affecting Stryker’s online services.

For the past week, the massive “Internet of Things” (IoT) botnet known as Kimwolf has been disrupting The Invisible Internet Project (I2P), a decentralized, encrypted communications network designed to anonymize and secure online communications. I2P users started reporting disruptions in the network around the same time the Kimwolf botmasters began relying on it to evade takedown attempts against the botnet’s control servers.

Kimwolf is a botnet that surfaced in late 2025 and quickly infected millions of systems, turning poorly secured IoT devices like TV streaming boxes, digital picture frames and routers into relays for malicious traffic and abnormally large distributed denial-of-service (DDoS) attacks.

I2P is a decentralized, privacy-focused network that allows people to communicate and share information anonymously.

“It works by routing data through multiple encrypted layers across volunteer-operated nodes, hiding both the sender’s and receiver’s locations,” the I2P website explains. “The result is a secure, censorship-resistant network designed for private websites, messaging, and data sharing.”

On February 3, I2P users began complaining on the organization’s GitHub page about tens of thousands of routers suddenly overwhelming the network, preventing existing users from communicating with legitimate nodes. Users reported a rapidly increasing number of new routers joining the network that were unable to transmit data, and that the mass influx of new systems had overwhelmed the network to the point where users could no longer connect.

I2P users complaining about service disruptions from a rapidly increasing number of routers suddenly swamping the network.

When one I2P user asked whether the network was under attack, another user replied, “Looks like it. My physical router freezes when the number of connections exceeds 60,000.”

A graph shared by I2P developers showing a marked drop in successful connections on the I2P network around the time the Kimwolf botnet started trying to use the network for fallback communications.

The same day that I2P users began noticing the outages, the individuals in control of Kimwolf posted to their Discord channel that they had accidentally disrupted I2P after attempting to join 700,000 Kimwolf-infected bots as nodes on the network.

The Kimwolf botmaster openly discusses what they are doing with the botnet in a Discord channel with my name on it.

Although Kimwolf is known as a potent weapon for launching DDoS attacks, the outages caused this week by some portion of the botnet attempting to join I2P are what’s known as a “Sybil attack,” a threat in peer-to-peer networks where a single entity can disrupt the system by creating, controlling, and operating a large number of fake, pseudonymous identities.

Indeed, the number of Kimwolf-infected routers that tried to join I2P this past week was many times the network’s normal size. I2P’s Wikipedia page says the network consists of roughly 55,000 computers distributed throughout the world, with each participant acting as both a router (to relay traffic) and a client.

However, Lance James, founder of the New York City based cybersecurity consultancy Unit 221B and the original founder of I2P, told KrebsOnSecurity the entire I2P network now consists of between 15,000 and 20,000 devices on any given day.

An I2P user posted this graph on Feb. 10, showing tens of thousands of routers — mostly from the United States — suddenly attempting to join the network.

Benjamin Brundage is founder of Synthient, a startup that tracks proxy services and was the first to document Kimwolf’s unique spreading techniques. Brundage said the Kimwolf operator(s) have been trying to build a command and control network that can’t easily be taken down by security companies and network operators that are working together to combat the spread of the botnet.

Brundage said the people in control of Kimwolf have been experimenting with using I2P and a similar anonymity network — Tor — as a backup command and control network, although there have been no reports of widespread disruptions in the Tor network recently.

“I don’t think their goal is to take I2P down,” he said. “It’s more they’re looking for an alternative to keep the botnet stable in the face of takedown attempts.”

The Kimwolf botnet created challenges for Cloudflare late last year when it began instructing millions of infected devices to use Cloudflare’s domain name system (DNS) settings, causing control domains associated with Kimwolf to repeatedly usurp Amazon, Apple, Google and Microsoft in Cloudflare’s public ranking of the most frequently requested websites.

James said the I2P network is still operating at about half of its normal capacity, and that a new release is rolling out which should bring some stability improvements over the next week for users.

Meanwhile, Brundage said the good news is Kimwolf’s overlords appear to have quite recently alienated some of their more competent developers and operators, leading to a rookie mistake this past week that caused the botnet’s overall numbers to drop by more than 600,000 infected systems.

“It seems like they’re just testing stuff, like running experiments in production,” he said. “But the botnet’s numbers are dropping significantly now, and they don’t seem to know what they’re doing.”