Cybersecurity vets protest ‘dangerous’ US government ban on Anthropic’s most powerful models

Published 15 June 2026 · tech

A group made up of dozens of cybersecurity experts, including several well-known veterans of the industry, published an open letter to the U.S. government asking

A group made up of dozens of cybersecurity experts, including several well-known veterans of the industry, published an open letter to the U.S. government asking it to lift the export control order on Anthropic’s Fable and Mythos models. According to the open letter, “this action has taken the best models away from [cybersecurity] defenders” who now can’t use the models to find vulnerabilities and make their software and products more secure. “To pull the best capabilities away from defenders without a good reason when our adversaries are rapidly advancing is dangerous,” read the letter. On Friday, the U.S. government ordered Anthropic to limit the export of Fable and Mythos citing national security concerns, without explaining the specific reasons behind the order, according to Anthropic. In response, the company suspended access to the models to all users worldwide. As of this writing, the letter is signed by 76 cybersecurity experts, including: former Facebook chief of security Alex Stamos; Casey Ellis, the founder bug bounty platform Bugcrowd; famed cryptographer and former Apple security design and architecture manager Jon Callas; computer scientist Paul Vixie; Dino Dai Zovi, the former head of applied security engineering at Block; Katie Mossouris, the founder of Luta Security; and Rachel Tobac, the CEO of the security awareness training firm SocialProof Security.

When Mythos launched as a preview in April, Anthropic claimed it was so powerful at finding security vulnerabilities that the company needed to tightly restrict access to prevent malicious hackers or foreign adversaries from using it to cause havoc on the internet. In practice, that meant Anthropic gave around 50 companies initial access to Mythos, recently expanding that group to include around 150 organizations in 15 countries. Last week, Anthropic released Fable, a public version of Mythos that the company said had strict guardrails to block its use in the fields of biology, chemistry, and cybersecurity, as well as to stop others from distilling the model in order to recreate it. The guardrails on Fable were so strict that many cybersecurity experts found that it stopped essentially any prompts related to cybersecurity. Anthropic said that the White House export control order may have been based on a report that there was a method to bypass — or so-called jailbreaking — Fable to unlock its powerful Mythos-level capabilities. Contact Us Do you have more information about the Amazon paper that prompted the ban?