Reuters Exclusive: Lone Hacker Used AI Agents to Breach 100+ Company Websites at About $50 Each

What happened

According to a Reuters exclusive on October 19, Snorre Fagerland, principal threat researcher at cybersecurity company NorForge, found about two dozen Cairn instances being used for malicious activity (starting around October 2) while scanning the web for inadvertently exposed instances of Cairn, an open-source AI problem-solving platform — letting him quietly 'peer over the cybercriminals' shoulders.' The Chinese-speaking hacker was the most prolific: starting September 25, they set their AI army loose against e-commerce websites in the US, Canada, Australia and Japan.

The hacker's instructions were terse: fewer than 100 Chinese characters sketching out preferred intrusion tactics. As of late last week, their agents had attempted to break into more than 1,200 sites; a successful intrusion typically took around 23 hours of probing for vulnerabilities. Fagerland estimated the campaign, which appeared to use a mixture of China's DeepSeek and Anthropic's Claude Code, had chewed up roughly $5,000 worth of tokens — about $50 per successful hack.

Fagerland said he was impressed by some of the agents' techniques: in one case, after failing to find weaknesses in a big company's public-facing application, the agents pored through digital records to find associated infrastructure, located a public-facing control panel, discovered a subtle weakness in how it processed data, and after hours of trial and error, tricked the server into executing malicious commands. Reuters independently reviewed the hacker's Cairn activity and established the victims' identities, including farm equipment maker Deere, home appliance company SharkNinja and engine manufacturer Cummins.

It's not straightforward to come up with solutions like that. It's not script kiddie stuff.

— Snorre Fagerland, principal threat researcher at NorForge (quoted in Reuters)

The victims responded: Deere said it had taken 'necessary remediation actions' with 'no indication that sensitive information was accessed'; SharkNinja said the hack hit a standalone site carrying only product support information and the threat had been contained; Cummins said it was investigating 'the report of a potential cyber-attack on a website operated by one of our third-party vendors'; two smaller businesses also acknowledged being compromised. Reuters could not ascertain whether the breaches led to data theft. Cairn's author (social handle 'le1xia0') acknowledged Reuters' message but did not immediately answer; on X they said the platform is 'an innovative type of multi-agent architecture and was not designed for hacking attacks,' and if used for harmful hacking attacks, 'that is not my intention.'

Key facts

1. How it was found: NorForge's Fagerland scanned the web for exposed Cairn instances and, starting around October 2, found about two dozen being used for malicious activity; one other hacker stole a trove of credit card data, and another tried to get agents to rob a cryptocurrency exchange.
2. Campaign scale: The Chinese-speaking hacker began on September 25; by late last week they had attempted break-ins at more than 1,200 sites and breached over 100 companies; a successful intrusion averaged about 23 hours of probing.
3. The cost math: A mixture of DeepSeek and Claude Code; roughly $5,000 in tokens; about $50 per successful hack.
4. Victims: Reuters' independent review confirmed Deere, SharkNinja and Cummins among them; Deere said there was no indication sensitive information was accessed; SharkNinja said it was a standalone support site and the threat was contained; Cummins said it was investigating a third-party vendor's site.
5. Industry backdrop: In August, Gambit Security found Russian-speaking extortionists using a Cursor AI tool to break into seven organizations; in September, an AI-agent crime spree breached 25 companies and stole at least 600,000 credit card records; last week, Bitsight said discussions about autonomous agents were surging across cybercriminal forums.