Pentagon Cyber Chief Says Anthropic Mythos Model Breached Nearly All Classified Networks in Hours

On June 11, Gen. Joshua Rudd, who heads the NSA and US Cyber Command, told Sen. Mark Warner that Mythos "broke into almost all of our classified systems, not in weeks, but in hours" during an authorized red-team exercise, per The Economist's June 14 report 1234; the quote reflects Warner's public account of a private briefing, not a direct Rudd statement. The next day, the Trump administration directed Anthropic to restrict Fable 5 and Mythos 5 to US citizens; Anthropic shut both models globally, unable to enforce nationality restrictions at scale, cutting off Five Eyes partners without warning 234. No government agency has confirmed the breach claim, and full details remain classified; Anthropic disputes the characterization, saying the test involved code analysis that surfaced only minor, already-known bugs, not autonomous offensive intrusion 23. The Economist's author Shashank Joshi subsequently clarified the Rudd quote should not be read literally, noting Mythos almost certainly worked alongside other tools under specific test conditions rather than as a standalone autonomous offensive capability 2.