The artificial intelligence (AI) firm Anthropic has blocked access to its newly released cutting-edge artificial intelligence software, following an order by the US government.
In a blog post published Friday, the company said government agencies had instructed it to prevent all foreign nationals from accessing the AI models Fable 5 and Mythos 5, citing national security concerns.
The ban also affects foreigners currently in the United States – including those working at Anthropic. As a result of the order, the company had to cut off access for everyone at short notice, it said.
The artificial intelligence behind Anthropic’s Mythos AI model is particularly adept at detecting software vulnerabilities, some of which have remained undiscovered for decades. This capability has so far been used by US authorities and selected companies to plug security gaps. However, a concern from the outset has been that such AI could become a dangerous cyberweapon in the wrong hands.
The Fable 5 model, released just this week, is based on Mythos technology, but its cybersecurity and biotechnology capabilities are blocked. Mythos 5 is the non-public full version, which should continue to be used only by government agencies and selected corporate partners to harden their systems.
Anthropic emphasized that it had so far received only partial information from the government. The company said it had reviewed a report which, in its assessment, was likely to have triggered the order. Anthropic's experts concluded that this referred to a limited capability to use the AI to review specific programme code and correct errors.
Models from other providers, such as GPT-5.5 from rival OpenAI, also possess this capability, the company stressed. Anthropic said it does not agree that software for hundreds of millions of users should be blocked for this reason, and said the safety measures in Fable 5 have been extensively tested.
Just a few days ago, Anthropic chief executive Dario Amodei spoke out in favour of the government blocking potentially dangerous AI software. Anthropic stresses, however, that this must be done on the basis of transparent and clear procedures as well as technical facts. That is not the case at present, it said.
Anthropic has repeatedly made headlines in recent months for clashing with the US administration. The firm previously insisted, despite pressure, that its AI models must not be used in autonomous weapon systems or for mass surveillance in the US.
The Pentagon subsequently declared Anthropic a supply chain risk, which could severely hamper the use of the company’s software within government agencies. The company is challenging this decision.
Mythos’s exceptional cybersecurity capabilities have since made Anthropic important to the US government once again.
