How to Fix Fix Error 0x80073B01 — Windows Defender or Security Error on Windows
Getting error 0x80073B01 when running Windows Defender scan, updating definitions, or enabling real-time protection? Fix this Windows Security error.
Symptoms
You might be experiencing this problem if you notice:
- •Windows Defender scan fails with error 0x80073B01
- •Can't enable real-time protection — error 0x80073B01
- •Defender definition update fails with this error
- •Windows Security shows "Your virus & threat protection is managed by your organization"
- •Quick Scan or Full Scan starts but immediately errors out
- •Error in Event Viewer: Windows Defender Antivirus encountered an error
Common Causes
- ⚠Windows Defender service files corrupted
- ⚠Third-party antivirus left remnants disabling Defender
- ⚠Group Policy or registry disabling Defender components
- ⚠Defender definition files corrupted
- ⚠Windows Security Center service not running
- ⚠SYSTEM or TrustedInstaller permissions changed on Defender folders
Solutions
Solution 1: Re-Register Defender Components
- 1CMD as Admin:
- 2regsvr32 wuaueng.dll
- 3regsvr32 wucltui.dll
- 4regsvr32 softpub.dll
- 5regsvr32 wintrust.dll
- 6regsvr32 initpki.dll
- 7regsvr32 wups.dll
- 8regsvr32 wuweb.dll
- 9regsvr32 atl.dll
- 10regsvr32 mssip32.dll
- 11Restart PC and try Defender again
Solution 2: Remove Third-Party AV Remnants
- 1If you recently uninstalled a third-party antivirus:
- 2Remnants may still be disabling Defender
- 3Download the vendor's removal tool:
- 4Norton: Norton Remove and Reinstall tool
- 5McAfee: MCPR (McAfee Consumer Product Removal)
- 6Kaspersky: kavremover
- 7Avast/AVG: avastclear utility
- 8Run the removal tool → restart → check if Defender activates
Solution 3: Fix via Registry and Group Policy
- 1Check if Defender is disabled by policy:
- 2Regedit → HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender
- 3If "DisableAntiSpyware" exists and = 1: change to 0 or delete it
- 4Also check: "DisableAntiVirus" — delete if present
- 5For Group Policy: gpedit.msc → Computer Configuration → Admin Templates
- 6→ Windows Components → Microsoft Defender Antivirus
- 7Set "Turn off Microsoft Defender Antivirus" to Not Configured
- 8Restart PC → Windows Security should now work
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