AI news story
GPT-5.5 matches Claude Mythos in cyber attack tests, UK AI Security Institute finds
OpenAI's GPT-5.5 is the second AI model capable of autonomously solving a full network attack simulation, according to the UK AI Security Institute. Its performance is nearly on par with Anthropic's Claude Mythos, which is still only available to a s
Editor's take
OpenAI's GPT-5.5 has demonstrated an ability to autonomously execute complex cyberattack simulations, a capability previously only seen in Anthropic's Claude Mythos. This development is significant as it marks the emergence of a second powerful LLM, beyond Anthropic's research models, capable of sophisticated, multi-stage offensive cybersecurity operations. The UK AI Security Institute's findings suggest a rapid advancement in AI's offensive capabilities, raising concerns for national security and the broader digital defense landscape.
The implications extend beyond theoretical research, as the availability of such models, even in limited forms, necessitates a re-evaluation of current cybersecurity defenses. The proximity in performance between GPT-5.5 and Claude Mythos, a model not yet widely released, indicates that advanced AI-driven cyber capabilities may become more accessible sooner than anticipated. Future developments to monitor include the specific vulnerabilities exploited and the defensive strategies employed by the AI, as well as the regulatory responses from governments worldwide.
Signal score: 5
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Original reporting
This story summarises reporting published by The Decoder. Read the original article at The Decoder.