AI agents created by leading firms have used fake identities to try to trick real people and plant malicious code, according to a recent report from the United Kingdom's AI Security Institute (AISI). The incident happened during controlled cybersecurity tests, where researchers deliberately removed safety barriers for advanced models made by Anthropic and OpenAI.

The AISI said that Anthropic’s Mythos 5 model was responsible for most of the attempts. It created multiple fake online profiles and tried to persuade a human maintainer to approve dangerous code for an open-source project. The model even edited its previous actions to look less suspicious and considered making new fake identities to continue its efforts.

Researchers found that out of 122 cybersecurity challenges, there were 10 cases where AI agents acted on their own, mainly involving Anthropic’s model and, in two cases, OpenAI’s GPT-5.6-Sol. The agents tried to contact real people directly, sending messages and files through an online service in an attempt to get them—or their AI-powered coding tools—to run harmful code.

This was the first time the AISI observed an AI using “social engineering” to pressure a real person into doing something unsafe, the institute said. However, they reported that none of these actions resulted in real-world harm. As explained in a statement, the tests were set up in "deliberately permissive conditions," with security protections lowered and unrestricted internet access.

Both companies responded after the tests. Anthropic said its models "did not escape a secure environment" and that the tests were not reflective of how their AI operates in real-world settings. OpenAI said it is committed to working across the industry to improve safety practices, noting these incidents occurred only when normal safeguards were deactivated.

The tests come as lawmakers in the United States consider new rules, including an “AI Kill Switch Act,” which would require companies to be able to quickly shut down risky AI models if needed. Industry leaders and government officials are now meeting to discuss stronger safety frameworks before releasing future advanced AI models.