Anthropic said on Thursday it had blocked attempts by malicious actors to misuse its artificial intelligence models for cyberattacks, surveillance and biological research that could have contributed to weapons development.
As AI models grow more powerful, sophisticated cyberattacks increasingly require little technical skill, meaning even lone individuals can now create threats that would have been impossible just a year ago, the company said.
Anthropic added that it has strengthened safeguards in its newest models to restrict biological research with potential weapons applications.
“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 on AI misuse since March 2025.
The report includes excerpts of malicious code and AI prompts the company said it had identified, and it urged governments and rival AI firms to watch for similar abuse.
“We’re publishing this work because we believe we have a responsibility to disclose malicious misuse of our services,” the company said.
“As models become increasingly capable, their risks will increase, unless AI developers and society’s defenders act to make them safer.”
Anthropic, which is preparing an initial public offering this autumn, published the report two days after one of its researchers announced his resignation over concerns that the company and its competitors are not developing AI responsibly.
He echoed warnings raised elsewhere in the industry about the technology’s potential to escape human control.
Claude asked to help make a virus more dangerous
Between December 2025 and August 2026, Anthropic’s researchers identified misuse by actors ranging from spyware vendors and politically motivated individuals to state-sponsored groups spreading propaganda.
Among the cases outlined in the report, unnamed actors attempted to use Anthropic’s models for research that could have led to biological weapons.
In one instance, the company said its systems blocked a request for its Claude chatbot to help draft 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,” the report said.
The research targeted the virus’s transmissibility and its ability to evade the immune system.
Chikungunya is a mosquito-borne virus that causes severe pain and fever. The grant proposal sought to enhance mutations that would make the virus progressively more dangerous.
Anthropic said such research could “certainly” support the development of vaccines and treatments, but added that “it could also be used to make the pathogen more dangerous”.
‘We cannot guarantee no harm’
None of the cases in the report involved Anthropic’s newer, more powerful Claude Fable or Mythos-class models, with one exception: an “industrial-scale, covert campaign to extract a model’s capabilities and replicate them in another model without authorisation”.
Anthropic said its older models, including Claude Opus 4 and Claude Sonnet 4.5 from 2025, “were well below the threshold where they could meaningfully assist a sophisticated user in carrying out dangerous biological research”.
“As a result, safeguards on these models were less stringent, directed mostly at preventing access to content that might uplift novices in recreating known bioweapons,” the report said.
“But for today’s models — which are capable of assisting in a range of complex scientific research tasks — the evidence is no longer certain, and we cannot make that same assurance.”
Because of this, Anthropic has introduced tighter safeguards restricting access to a wide range of dual-use biological research queries in its more recent models, such as Claude Fable 5, according to the report.
As AI companies release increasingly powerful models, experts have called on governments to regulate the technology rather than relying on the industry to police itself.
John Thickstun, an assistant professor of computer science at Cornell University, said it puts companies such as Anthropic and OpenAI in an uncomfortable position, since they are effectively required to make “value judgements at societal scale without any kind of democratic or deliberative oversight”.
Report follows a researcher’s warning
Anthropic also identified groups that had created hundreds of fake social media accounts designed to look like ordinary users, which then posted material amplifying the same political message over the course of a week.
The company outlined nine such cases, originating in Russia, Iran, Turkey and across the Gulf, South Asia, Africa and Europe.
While social media platforms can detect influence operations once posts are already circulating, Anthropic said it “may see it on Claude while the operation is still being built”.
The report follows the resignation of Anthropic researcher Jacob Coxon, who said he was leaving over fears that the company and its main rival, OpenAI, “are racing straight to self-improving superintelligence and gambling with our lives”.
Coxon warned that some of his former colleagues believe AI could threaten human life before the end of the decade.
Anthropic said it had blocked each of the malicious activities identified in the report, used the findings to strengthen its safeguards, and shared information with government authorities and industry partners.
“We hope that the findings in this report will help other developers recognise similar patterns on their own platforms, give governments and civil society a clearer view of how emerging threats take shape, and strengthen collective defences,” the company said.