# Anthropic says it blocked five Claude misuse cases tied to bioweapon research

_Friday, September 11, 2026 at 6:00 AM EDT · AI, Security · Developing · Tier 2 — Notable_

![Anthropic says it blocked five Claude misuse cases tied to bioweapon research — Primary](https://cdn.mos.cms.futurecdn.net/g4nXrCZY8SaCBTKgyPUXVW-2371-80.jpg)

Anthropic disclosed five cases, drawn from activity between November 2025 and September 2026, in which users asked Claude to assist work it assessed as potentially usable in biological weapons.

Three involved viruses, including chikungunya and avian flu research, and two involved toxins, according to the company's report. Anthropic said the accounts used anonymization, gray-market resellers and U.S.-routed traffic to evade regional blocks, and that it banned the accounts and shared information with government authorities.

The report does not name specific states. Anthropic said it launched recent models with stronger safeguards out of caution.

## Sources

- [Tom's Hardware](https://www.tomshardware.com/tech-industry/artificial-intelligence/anthropic-says-claude-thwarted-bioweapon-research-from-state-sponsored-actors-covert-accounts-used-u-s-proxies-to-attempt-to-engineer-deadlier-viruses-tried-to-evade-identification-and-regional-blocks)
- [Ars Technica](https://arstechnica.com/ai/2026/09/claude-users-found-ways-around-safeguards-for-bioweapons-research/)

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Retrieved: 2026-09-12T04:07:11.776Z
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