Security News > 2023 > July > Hackers Exploit Windows Policy Loophole to Forge Kernel-Mode Driver Signatures

A Microsoft Windows policy loophole has been observed being exploited primarily by native Chinese-speaking threat actors to forge signatures on kernel-mode drivers.

"Actors are leveraging multiple open-source tools that alter the signing date of kernel mode drivers to load malicious and unverified drivers signed with expired certificates," Cisco Talos said in an exhaustive two-part report shared with The Hacker News.

The new weakness discovered by Cisco Talos makes it possible to forge signatures on kernel-mode drivers, thereby allowing Windows certificate policies to be bypassed.

"The third exception creates a loophole that allows a newly compiled driver to be signed with non-revoked certificates issued prior to or expired before July 29, 2015, provided that the certificate chains to a supported cross-signed certificate authority," the cybersecurity company said.

As a result, a driver signed in this manner will not be prevented from being loaded on a Windows device, thereby enabling threat actors to take advantage of the escape clause to deploy thousands of malicious, signed drivers without submitting them to Microsoft for verification.

"HookSignTool is a driver signature forging tool that alters the signing date of a driver during the signing process through a combination of hooking into the Windows API and manually altering the import table of a legitimate code signing tool," Cisco Talos explained.

News URL

https://thehackernews.com/2023/07/hackers-exploit-windows-policy-loophole.html