Tracking a stolen code-signing certificate with osquery

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Updated 11 March 2025

Recently, 2.27 million computers running Windows were infected with malware signed with a stolen certificate from the creators of a popular app called CCleaner, and inserted into its software update mechanism. Fortunately, signed malware is now simple to detect with osquery thanks to a pull request submitted by our colleague Alessandro Gario that adds Windows executable code signature verification (also known as Authenticode). This post explains the importance of code signatures in incident response, and demonstrates a use case for this new osquery feature by using it to detect the recent CCleaner malware. If you are unfamiliar with osquery, take a moment to read our previous blog post in which we explain why we are osquery evangelists, and how we extended it to run on the Windows platform. Part of osquery’s appeal is its flexibility and open-source model – if there’s another feature you need built, let us know! Code-signed malware Code signing was intended to be an effective deterrent against maliciously modified executables, and to allow a user (or platform owner) to choose whether to run executables from untrusted sources. Unfortunately, on general-purpose computing platforms like Windows, third-party software vendors are individually responsible for protecting thei