Anthropic Says a Yemen Cell Used Claude Code as Its Engineers

A weapons-development cell in northern Yemen used Claude Code "in place of human software engineers" to build guidance software for rockets and missiles, Anthropic said in a threat intelligence report published Sept. 10.

Anthropic disrupted the operation, banned the accounts involved and shared intelligence with government and industry partners, according to the report, which the company labeled case GTG-87001. The cell operated in territory largely controlled by Yemen's Houthi movement, though Anthropic did not identify the actors by that name.

Three weapons programs, one field test

Anthropic described three separate programs: "a guided rocket that used a commodity phone-class flight computer with final-phase homing guidance; a multi-stage ballistic missile with a stated range goal above 2,000 km; and a multi-variant missile (referred to as the 'R2000' set) that included a hypersonic glide vehicle variant."

The actors ran several Claude instances at once, Anthropic said, assigning one to write code, another to research and a third to review the first instance's output, a division of labor the company compared to a lead delegating work on a small engineering team.

Safeguards blocked many requests, not all

Anthropic said its safeguards blocked many of the cell's requests but not every one. The actors concealed their ultimate goals and split the work across many sessions, according to the report, so no single conversation exposed the program's full scope.

Anthropic said the cell test-fired a guided rocket in what appears to have been a failed launch, then came back to Claude within hours, asking it to help figure out the cause.

Anthropic said it has no evidence the cell fielded a working weapon. But the company did find the group had already packaged its own offline simulation toolkit, a standalone piece of software that runs without Claude or tools like MATLAB, meaning the ban did not erase everything the cell built.

A wider pattern across three countries

The Yemen case was one of six weapons-development investigations in the September report, which also covered three cases in China and two in Russia, including a Russia-based effort to build an autonomous drone swarm the actors called "Serafim." The report's seventh harm area, distillation, follows a Sept. 8 advisory naming six China-based AI firms that CISA, the NSA and FBI said had copied Claude, GPT, Gemini and Grok since late 2024.

Two days after the weapons report, Anthropic chief executive Dario Amodei called for an industry-wide slowdown, citing a separate incident involving Hugging Face.

Country	Weapons cases in the report	Example system described
Yemen	1	Guided rocket with a phone-class flight computer
China	3	16-module electronic-warfare suite
Russia	2	"Serafim" autonomous drone swarm

Anthropic said it has since deployed new classifiers designed to better detect and block traffic related to high-yield explosives and weapons development, according to IBTimes UK, which first tied the Yemen cell's territory to the Houthi movement.