• 5 min read

Deploy, Test, Monitor: Mastering Microsoft AppLocker (Part 1)

Part 1 of the AppLocker series covering deployment strategies, policy creation, and testing methodologies for effective application whitelisting.

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Originally published on the Splunk Security Blog
Read the full article: Mastering Microsoft AppLocker Part 1

Why AppLocker?

Application whitelisting is one of the most effective security controls available. AppLocker lets you define exactly which applications can run—and block everything else.

AppLocker Rule Types

  1. Executable Rules - Control .exe and .com files
  2. Windows Installer Rules - Control .msi and .msp files
  3. Script Rules - Control .ps1, .bat, .cmd, .vbs, .js
  4. Packaged App Rules - Control Windows Store apps
  5. DLL Rules - Control .dll and .ocx files

Deployment Strategy

Phase 1: Audit Mode

Start with audit mode to understand your environment:

# Enable audit mode for executables
Set-AppLockerPolicy -PolicyObject $policy -Merge

Phase 2: Analyze Logs

index=windows source="WinEventLog:Microsoft-Windows-AppLocker/*"
| stats count by RuleName, FilePath, UserName
| sort -count

Phase 3: Refine Rules

Based on audit data, create allow rules for legitimate applications.

Phase 4: Enforce

Switch from audit to enforce mode.

Rule Best Practices

  • Use publisher rules when possible (survive updates)
  • Path rules for trusted directories
  • Hash rules as last resort (break on updates)
  • Never block administrators until you’re confident

Common Pitfalls

  • Blocking legitimate admin tools
  • Not accounting for software updates
  • Missing DLL rules (if enabled)
  • Forgetting about scripts

Continue to Part 2 for testing and monitoring strategies.

Read the full guide: Mastering Microsoft AppLocker Part 1

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