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Evaluation of Claude Mythos Preview's cyber capabilities

aisi.gov.uk

April 13, 2026

1 min read

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44/100

Summary

Claude Mythos Preview shows improved performance in capture-the-flag (CTF) challenges and significant advancements in multi-step cyber-attack simulations. The evaluation indicates enhanced cyber capabilities compared to previous versions.

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Community Sentiment

Mixed

Positives

Mythos is the first model to complete all steps of 'The Last Ones' evaluation, showcasing significant advancements in automated network takeover capabilities.
The evaluation indicates continued improvement in capture-the-flag challenges and notable enhancements in multi-step cyber-attack simulations, suggesting a positive trajectory for AI in cybersecurity.

Concerns

Despite some improvements, the performance metrics suggest that Mythos only marginally outperforms previous models like Opus 4.6, raising questions about its overall impact.
The lack of active defenders in the evaluation raises concerns about the real-world applicability of the results, as actual networks have security teams that could thwart such attacks.
The absence of confidence intervals in the evaluation undermines the claims of significant improvement, highlighting a need for more rigorous statistical analysis in AI assessments.