UK Institute Finds Mythos Seizes Corporate Networks in 60% of Tests, GPT-5.5 in 30%
Updated
Updated · POLITICO · May 24
UK Institute Finds Mythos Seizes Corporate Networks in 60% of Tests, GPT-5.5 in 30%
1 articles · Updated · POLITICO · May 24
Summary
Mythos fully took over a corporate network in 6 of 10 UK AI Security Institute tests, while GPT-5.5 succeeded in 3 of 10.
Those results underscore how quickly frontier models' cyber capabilities are improving, with British AI Minister Kanishka Narayan saying the advance is faster than expected.
Broadcom, which tested Mythos against its own software code, called the findings "jolting" and said the model was uncovering issues unlikely to have been found by human researchers alone.
The same capability could help defenders catch bugs before software is released, but officials and researchers warn it may give attackers and state-backed hackers the bigger near-term advantage.
China's push to copy U.S. AI through large-scale distillation attacks is adding to fears that rival states could soon field similarly powerful cyber models.
With AI automating cyberattacks, can human-led defenses possibly keep pace?
Is China's open-source AI strategy a power play or a move that recklessly arms the world?
AI Models Surpass Human Experts in Cyberattack Simulations: Anthropic Claude Mythos and OpenAI GPT-5.5 Achieve Breakthroughs in 2026
Overview
In April 2026, the UK AI Security Institute reported a major breakthrough in AI's ability to carry out cyberattacks autonomously. Anthropic’s Claude Mythos Preview became the first AI to fully complete a complex corporate network attack simulation, solving tough challenges like 'The Last Ones' and the previously unsolved 'Cooling Tower.' OpenAI’s GPT-5.5 also showed similar high-level performance. These results mark the first time any AI has mastered both of AISI’s most difficult cyber ranges, highlighting a rapid and significant leap in AI-driven offensive cybersecurity capabilities.