Anthropic Unveils ‘Claude Mythos’ – A Cybersecurity Breakthrough That Could Also Supercharge Attacks

Anthropic may have just announced the future of AI – and it is both very exciting and very, very scary. Mythos is the Ancient Greek word that eventually gave us ‘mythology’. It is also the name for Anthropic’s latest foundational AI Model: it evokes the connective tissue that links together knowledge and ideas. Industry excitement over Anthropic’s Claude Mythos began at the end of March 2026 when Fortune magazine published information on an upcoming Anthropic development. The information came from a leak of almost 3,000 files from a misconfigured CMS. Anthropic confirmed the details.  Today, less than two weeks after the Fortune publication, Anthropic officially announced Mythos Preview as the basis of Project Glasswing. Mythos is not an incremental improvement but a step change in performance over Anthropic’s current range of frontier models: Haiku (smallest), Sonnet (middle ground), and Opus (most powerful). Mythos sits in a fourth tier named Copybara, and Anthropic describes it as superior to any other existing AI frontier model. It incorporates the current trend in the use of AI: the modern use of agentic AI. “The powerful cyber capabilities of Claude Mythos Preview are a result of its strong agentic coding and reasoning skills… the model has the highest scores of any model yet  developed on a variety of software coding tasks,” notes Anthropic in a blog titled  Project Glasswing – Securing critical software for the AI era. Project Glasswing Anthropic is historically cautious – as witnessed by its current impasse with the Pentagon. Like other AI frontier model developers, it does not develop AI for cybersecurity specifically, but for the benefit of science and society. Nevertheless, it is fully aware of its potential misuse by cybersecurity adversaries. This potential is magnified by the power of Mythos. In the last few weeks, Mythos Preview has identified thousands of zero-day vulnerabilities with many classified as critical. Several are ten or 20 years old – the oldest found so far is a 27-years old bug in OpenBSD. Elsewhere, a 16-years old vulnerability found in video software has survived five million hits from other automated testing tools without ever being discovered. And it autonomously found and chained together several in the Linux kernel allowing an attacker to escalate from ordinary user access to complete control of the machine. While Anthropic’s long term intent is to make Mythos available to as many people as possible, the danger with this level of cybersecurity power in the wrong hands is self-evident. In November 2025, Anthropic blogged about ‘the first reported AI-orchestrated cyber espionage campaign’. “In mid-September 2025, we detected suspicious activity that later investigation determined to be a highly sophisticated espionage campaign. The attackers used AI’s ‘agentic’ capabilities to an unprecedented degree – using AI not just as an advisor, but to execute the cyberattacks themselves. The threat actor – whom we assess with high confidence was a Chinese state-sponsored group – manipulated our Claude Code…” Anthropic is concerned that Mythos’ capabilities could unleash cyberattacks too fast and too sophisticated for defenders to block. It hopes that Mythos can be used to improve cybersecurity generally before malicious actors can get access to it. To this end, the firm has announced the next stage of this preparation as Project Glasswing, powered by Mythos Preview. Given the rate of AI progress, it will not be long before such capabilities proliferate, potentially beyond actors who are committed to deploying them safely. “Project Glasswing is a starting point. No one organization can solve these cybersecurity problems alone: frontier AI developers, other software companies, security researchers, open-source maintainers, and governments across the world all have essential roles to play.” Claude Mythos Preview is described as a general-purpose, unreleased frontier model from Anthropic that has nevertheless completed its training phase. The firm does not plan to make Mythos Preview generally available. The implication is that ‘Preview’ is a term used solely to describe the current state of Mythos and the market’s readiness to receive it, and will be dropped when the firm gets closer to general release. Glasswing brings together Amazon, Anthropic, Apple, Broadcom, Cisco, CrowdStrike, the Linux Foundation, Microsoft, and Palo Alto Networks in an effort to secure the world’s most critical software. “The work of defending the world’s cyber infrastructure might take years; frontier AI capabilities are likely to advance substantially over just the next few months. For cyber defenders to come out ahead, we need to act now.” Anthropic is also extending access, outside of Project Glasswing, to more than 40 other organizations that build or maintain critical software, “so they can use the model to scan and secure both first-party and open-source systems.” From the Glasswing partners, Igor Tsyganskiy, EVP of cybersecurity and Microsoft research, comments, “Joining Project Glasswing, with access to Claude Mythos Preview, allows us to identify and mitigate risk early and augment our security and development solutions so we can better protect customers and Microsoft.” Cisco’s SVP & chief security & trust officer, Anthony Grieco, says, “The old ways of hardening systems are no longer sufficient. Providers of technology must aggressively adopt new approaches now, and customers need to be ready to deploy. That is why Cisco joined Project Glasswing – this work is too important and too urgent to do alone.” Elia Zaitsev, CTO at CrowdStrike, adds, “Claude Mythos Preview demonstrates what is now possible for defenders at scale, and adversaries will inevitably look to exploit the same capabilities. That is not a reason to slow down; it’s a reason to move together, faster. If you want to deploy AI, you need security. That is why CrowdStrike is part of this effort from day one.” And Jim Zemlin, CEO at the Linux Foundation, says “Open source maintainers—whose software underpins much of the world’s critical infrastructure—have historically been left to figure out security on their own… By giving the maintainers of these critical open source codebases access to a new generation of AI models that can proactively identify and fix vulnerabilities at scale, Project Glasswing offers a credible path to changing that equation.” Learn More at the AI Risk Summit | Ritz-Carlton, Half Moon Bay Related: Critical Vulnerability in Claude Code Emerges Days After Source Leak Related: Trump Orders All Federal Agencies to Phase Out Use of Anthropic Technology Related: Anthropic Refuses to Bend to Pentagon on AI Safeguards as Dispute Nears Deadline Related: Anthropic Says Claude AI Powered 90% of Chinese Espionage Campaign WRITTEN BY Kevin Townsend Kevin Townsend is a Senior Contributor at SecurityWeek. He has been writing about high tech issues since before the birth of Microsoft. For the last 15 years he has specialized in information security; and has had many thousands of articles published in dozens of different magazines – from The Times and the Financial Times to current and long-gone computer magazines. 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