The Cybersecurity and Infrastructure Security Agency doesn't have access to Anthropic's powerful new Mythos Preview model , even though some other government agencies are using it, two sources tell Axios. Why it matters: The country's top cyber defense agency, tasked with helping to secure everything from banks to power plants, is on the outside looking in at a time when the industries it works with are deeply concerned about AI-powered cyberattacks overwhelming their defenses. Anthropic decided against a public release of Mythos due to its unprecedented ability to quickly discover and exploit security vulnerabilities. Instead, Anthropic provided it to more than 40 companies and organizations who are now testing it and working to shore up their systems. CISA is not on that list, the sources say. State of play: Earlier this month, an Anthropic official told Axios the company briefed CISA and the Commerce Department on Mythos' capabilities.…