Detect Unsigned or DevSigned Appx Package Installation
This rule detects the installation of AppX or MSIX packages, specifically looking for installations initiated by PowerShell that are either developer-signed (EventID 855) or unsigned (EventID 603 with specific flags). It filters out known legitimate Microsoft packages to reduce false positives. The rule correlates PowerShell process events with device events related to AppX/MSIX installations within a 30-seconds window.
Microsoft Sentinel (KQL)
