GPT-5.5 Matches Mythos Preview in Cybersecurity Capabilities
In a significant development in the realm of artificial intelligence and cybersecurity, OpenAI's GPT-5.5 has demonstrated capabilities on par with the much-anticipated Mythos Preview from Anthropic. This breakthrough, documented in recent tests by the UK’s AI Security Institute (AISI), could signal a shift in how AI models are perceived and utilized in cybersecurity applications.
Last month, Anthropic launched its Mythos Preview with considerable fanfare, suggesting a revolutionary leap in cybersecurity capabilities. However, the AISI's recent evaluation reveals that OpenAI's GPT-5.5, released to the public just last week, is on equal footing with Mythos Preview in terms of performance on various cybersecurity challenges.
Performance in Capture the Flag Challenges
The AISI has been rigorously testing frontier AI models since 2023 through a series of 95 Capture the Flag challenges. These tests are designed to evaluate the AI's ability to handle complex cybersecurity tasks such as reverse engineering, web exploitation, and cryptography.
In these tests, GPT-5.5 excelled, achieving an average success rate of 71.4% on the highest-level 'Expert' tasks. This is slightly ahead of the 68.6% success rate achieved by Mythos Preview, although the difference falls within the margin of error. A notable highlight was GPT-5.5's ability to construct a disassembler to decode a Rust binary in just over 10 minutes, with no human intervention, costing only $1.73 in API calls.
Advancements in Long-Horizon Autonomy
The parity between GPT-5.5 and Mythos Preview suggests that the latter's perceived superiority may not be a result of unique breakthroughs but rather a reflection of broader advancements in AI's long-horizon autonomy, reasoning, and coding capabilities. The AISI's findings imply that both models benefit from these general improvements, which are reshaping the capabilities of AI in cybersecurity.
In further tests, both models were evaluated on 'The Last Ones' (TLO), a challenging 32-step data extraction attack simulation. GPT-5.5 succeeded in three out of ten attempts, while Mythos Preview managed two out of ten, marking the first successes ever recorded on this test. However, both models faltered in the 'Cooling Tower' simulation, a complex scenario designed to test AI's ability to disrupt control software at a power plant, a challenge that remains unresolved by any AI model to date.
Reactions and Industry Implications
The results of these tests have sparked reactions from industry leaders. OpenAI CEO Sam Altman has voiced criticism toward what he describes as 'fear-based marketing' strategies, particularly in relation to the launch of AI models like Mythos Preview. Altman suggests that marketing tactics which emphasize fear can distort the public's perception of AI capabilities and potential threats.
Despite acknowledging Mythos Preview as a formidable model for cybersecurity, Altman argues that the marketing narrative of a 'pending threat' coupled with the sale of protective solutions can be misleading. He anticipates more discourse around models deemed 'too dangerous to release,' which may necessitate alternative release strategies.
OpenAI's Strategic Moves
In light of these developments, OpenAI has been proactive in managing access to its advanced AI models. Earlier this year, the company introduced its Trusted Access for Cyber pilot program. This initiative allows verified security researchers and enterprises to explore OpenAI's frontier models for legitimate defensive purposes.
OpenAI recently utilized this trusted access list to control the release of GPT-5.4-Cyber, a variant specifically fine-tuned for enhanced cybersecurity capabilities. Building on this strategy, OpenAI plans to limit the initial release of GPT-5.5-Cyber to critical cyber defenders, ensuring its capabilities are employed within secure and ethical boundaries.
A Look Ahead
The revelation that GPT-5.5 can match the capabilities of the Mythos Preview underscores the rapid advancements occurring in AI technology. As AI continues to evolve, its role in cybersecurity will likely expand, influencing how organizations approach threat detection and prevention.
Moving forward, stakeholders in the AI and cybersecurity sectors will need to navigate these technological advancements carefully, balancing innovation with ethical considerations and security protocols. As new models emerge, the landscape of cybersecurity will continue to be reshaped by AI, presenting both challenges and opportunities for developers, researchers, and industry leaders alike.