WDAC FilePath Rules and Drivers

The new File Path rules in Windows Defender Application Control (WDAC) allow EXE and DLL files in the path, but not SYS, or MSI or script files. This is curious and, as far as I know, undocumented. And it means that we cannot simply allow all files in C:\Windows. If we do that, the system will not boot because the drivers will still be blocked. We will need to use another method to add drivers to a WDAC policy.

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MDAC or WDAC

The Application Control feature in Windows 10 was originally called Device Guard Code Integrity. This was brought under the Defender umbrella of security technologies as Windows Defender Application Control (WDAC). Microsoft earlier this year announced that Windows Defender would become cross-platform (with a version of Defender antivirus for macOS) and be renamed Microsoft Defender.

In my blog posts I originally called it Microsoft Defender Application Control (MDAC). You can see in the screenshot below that all the Defender technologies for Windows 10 Endpoint Protection, in Intune, are now Microsoft Defender.

Intune Endpoint Protection Policies

However, Microsoft now seems to have standardised on WDAC, so I have reverted to that (2021).

Getting Started with WDAC

Windows Defender Application Control (WDAC) is the native Windows 10 security feature to control what files can be executed on the desktop. In Windows 1903, Microsoft has added support for file path rules as a basis for whitelisting. Before this, implementing a WDAC policy for the desktop in production was very difficult, almost impractical. File path rules allow applications in the Windows and Program Files folders to run without first specifying what they are. This is one of a series of posts about how to create and implement a WDAC policy for the desktop, with file path rules, and using Intune to deliver it.

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