CTS-Labs, following up on Tuesday's "Masterkey" exploit proof-of-concept video, posted a guide to bypassing Windows Credential Guard on an AMD Ryzen-powered machine. We once again begin in a privileged shell session, of an AMD-powered machine whose Secure Processor that has been compromised using admin privileges, by exploiting it using any of the 13 vulnerabilities chronicled by CTS-Labs. Mimikatz, a tool that is used by hackers to steal network credentials, should normally not work on a machine with Windows Credential Guard enabled. Using a modified version of Mimikatz, the CTS-Labs researchers are able to bypass Windows Credential Guard (which relies on hardware-level security features present on the processor), leveraging the AMD Secure Processor malware microcode they wrote.The proof-of-concept video follows.

Yesterday, we had a very productive phone call with CTS-Labs, the firm behind the "AMD Flaws" critical security vulnerabilities exposé of the "Zen" microarchitecture. Our questions focus on the practicality of exploiting these vulnerabilities, and should provide more insight to the skepticism centered on needing admin privileges, flashing BIOS ROMs, and other localized hacks that would render any machine, not just "Zen" powered, vulnerable. Feel free to follow up with questions in the comments section, if we can help explain something.

Security researchers with Israel-based CTS-Labs, have discovered a thirteen security vulnerabilities for systems based on AMD Zen processors. The thirteen new exploits are broadly classified into four groups based on the similarity in function of the processor that they exploit: "Ryzenfall," "Masterkey," "Fallout," and "Chimera."

The researchers "believe that networks that contain AMD computers are at a considerable risk," and that malware can "survive computer reboots and re-installations of the operating system, while remaining virtually undetectable by most endpoint security solutions," such as antivirus software. They also mention that in their opinion, "the basic nature of some of these vulnerabilities amounts to complete disregard of fundamental security principles. This raises concerning questions regarding security practices, auditing, and quality controls at AMD."