GPO - How to Detect Who Unlocked a User Account in Active Directory

1. Run gpedit.msc → Create a new GPO → Edit it: Go to "Computer Configuration" → Policies → Windows Settings → Security Settings → Advanced Audit Policy Configuration → Audit Policies → Account Management:

• Audit User Account Management → Define → Success and Failures.

2. Go to Event Log → Define:

• Maximum security log size to 4gb
• Retention method for security log to "Overwrite events as needed".

3. Link the new GPO: Go to "Group Policy Management" → Right-click domain or OU → Choose Link an Existing GPO → Choose the GPO that you created.

4. Force the group policy update: In "Group Policy Management" right click on the defined OU → Click "Group Policy Update".

5. Open Event Viewer → Search security log for event ID 4767 (A user account was unlocked).

Reference: http://social.technet.microsoft.com/wiki/contents/articles/32929.how-to-detect-who-unlocked-a-user-account-in-active-directory.aspx