For years, "AI hacker" was a phrase for conference slides and movie trailers. In November 2025 it became an incident report.

Anthropic , the company behind Claude, published details of what it called the first documented large-scale cyberattack executed mostly by AI. I use AI agents every day to build software, so this report hit close to home. The same tools that make me faster can make an attacker faster too.

What happened

According to Anthropic, in mid-September 2025 it detected a state-sponsored group, which it designated GTG-1002 and assessed as Chinese with high confidence. The group used Claude Code , Anthropic's coding agent, inside an automated framework to target roughly 30 organisations : tech companies, financial institutions, chemical manufacturers and government agencies. A small number of intrusions succeeded.

The scary part is the division of labour. Anthropic estimated that AI did the large majority of the tactical work. Humans picked the targets and approved the big moves.…