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148: WDAC / App Control

Implementation Effort: High — application allow-listing requires discovery, piloting, exception handling, and sustained operational ownership.

User Impact: Medium to High — when deployed well it reduces attack surface significantly, but mistakes can block legitimate apps, scripts, or drivers.

Overview​

App Control for Business, formerly widely referred to as Windows Defender Application Control (WDAC), is a strong Zero Trust endpoint control for allowing only trusted code to run. It is especially valuable on high-value devices, admin workstations, kiosks, and other tightly managed endpoints where reducing arbitrary code execution materially lowers risk. Because application control can break business processes when implemented hastily, the most important design principle is staged deployment with visibility before enforcement.

Implementation Guidance​

  • Use discovery and inventory first. Identify which applications, scripts, drivers, installers, and update mechanisms are actually required before building an allow policy.
  • Start with audit mode on pilot devices so you can observe what would be blocked and tune the policy before moving to enforcement.
  • Choose rule strategies carefully, such as signer-based trust, managed installer, intelligent security graph support where appropriate, path rules only when justified, and separate handling for scripts or drivers.
  • Deploy policies with Intune using the current supported management model for App Control for Business, and document any custom OMA-URI or XML-based components if they are still needed in your environment.
  • Define an exception workflow and emergency recovery path so a blocked business-critical app does not force administrators to dismantle the control globally.
  • Review audit and enforcement events regularly and integrate the findings into software onboarding and patch-management processes.

Reference​