Anthropic warns Claude misuse may have led to biological weapons development

Anthropic has said it blocked efforts , surveillance, and research that could have led to the development of biological weapons. As AI models grow more powerful, elaborate cyberattacks no longer require sophisticated skills, and even lone individuals can create threats that would not have been possible even a year ago, Anthropic said on Thursday. The company said it has added stronger safeguards in its latest models to restrict biological research that could also be used to make weapons. “The cases we share here aren’t typical misuse, but rather examples of the most notable and novel threat activity we’ve identified to date,” Anthropic said in its third report since March 2025 describing AI misuse. The report includes snippets of the malicious code and AI prompts Anthropic said it found, and urges governments and AI competitors to identify and prevent similar abuse. open image in gallery Claude AI website is seen on a laptop () “We’re publishing this work because we believe we have a responsibility to disclose malicious misuse of our services. As models become increasingly capable, their risks will increase, unless AI developers and society’s defenders act to make them safer,” the company said. The lengthy report , which is planning an initial public offering this fall, was published the day after one of its researchers announced he's resigning over concerns that Anthropic and its competitors are not acting responsibly in AI development. He echoed concerns raised inside and outside of the industry about the technology’s potential to elude human control. Between December 2025 and August 2026, researchers at Anthropic found misuse “politically motivated individuals” to state-sponsored groups spreading propaganda. open image in gallery Anthropic co-founder Tom Brown () Among the findings in the company's report are unnamed actors attempting to use its models for research that could have led to biological weapons. In one instance, Anthropic said its systems blocked a request for Claude’s assistance in authoring a grant application for scientific funding. “The work discussed in the application involved gain-of-function research (that is, research that genetically alters an organism to create a new or enhanced biological property) on the chikungunya virus. This gain-of-function research was aimed at the virus’ transmissibility and immune evasion properties,” the report said. Chikungunya is a mosquito-borne virus that causes debilitating symptoms such as severe pain and fever. The request involved a grant proposal for research seeking to enhance mutations to make the virus progressively more harmful.