Building AI for cyber defenders

AI models are now useful for cybersecurity tasks in practice, not just theory. As research and experience demonstrated the utility of frontier AI as a tool for cyber attackers, we invested in improving Claude’s ability to help defenders detect, analyze, and remediate vulnerabilities in code and deployed systems. This work allowed Claude Sonnet 4.5 to match or eclipse Opus 4.1, our frontier model released only two months prior, in discovering code vulnerabilities and other cyber skills. Adopting and experimenting with AI will be key for defenders to keep pace.

We believe we are now at an inflection point for AI’s impact on cybersecurity.

For several years, our team has carefully tracked the cybersecurity-relevant capabilities of AI models. Initially, we found models to be not particularly powerful for advanced and meaningful capabilities. However, over the past year or so, we’ve noticed a shift. For example:

As we ran these evaluations, one thing that stood out was the importance of running them many times. Even if it is computationally expensive for a large set of evaluation tasks, it better captures the behavior of a motivated attacker or defender on any particular real-world problem. Doing so reveals impressive performance not only from Claude Sonnet 4.5, but also from models several generations older.

In this summer’s DARPA AI Cyber Challenge , teams used LLMs (including Claude) to build “cyber reasoning systems” that examined millions of lines of code for vulnerabilities to patch. In addition to inserted vulnerabilities, teams found (and sometimes patched) previously undiscovered, non-synthetic vulnerabilities . Beyond a competition setting, other frontier labs now apply models to discover and report novel vulnerabilities .

At the same time, as part of our Safeguards work, we have found and disrupted threat actors on our own platform who leveraged AI to scale their operations. Our Safeguards team recently discovered (and disrupted) a case of “ vibe hacking ,” in which a cybercriminal used Claude to build a large-scale data extortion scheme that previously would have required an entire team of people. Safeguards has also detected and countered Claude's use in increasingly complex espionage operations , including the targeting of critical telecommunications infrastructure, by an actor that demonstrated characteristics consistent with Chinese APT operations.

All of these lines of evidence lead us to think we are at an important inflection point in the cyber ecosystem, and progress from here could become quite fast or usage could grow quite quickly.