Windows – Cannot turn on Windows Defender virus protection

windows 10windows-defender

Why can't I turn on Windows Defender virus protection?

Today I noticed that my Windows Defender virus protection was off. I've been through countless blog entries, articles, and forums but I can't find anything that makes a difference.

I'm running Windows 10, Version 1803 (OS Build 17134.345)

I don't have any other antivirus software installed.

Here's the warning in Control Panel's Security and Maintenance section:

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Clicking "Turn on now" brings up this blank Security Center window:

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Under "Virus & threat protection", if I click "Scan now" nothing happens. If I click "Run a new advanced scan", then "Custom scan", then "Scan now" it'll prompt me to select a directory, but nothing happens after that.

Group Policy Editor
Computer Configuration > Administrative Templates > Windows Components > Windows Defender Antivirus is still "Not configured"

HKLM/SOFTWARE/Microsoft/Windows Defender -> DisableAntiSpyware
HKLM/SOFTWARE/Microsoft/Windows Defender -> DisableAntiVirus

  • both set to 0

Command Prompt

  • DISM.exe /Online /Cleanup-image /Restorehealth didn't report any problems
  • sfc /scannow did find and repair corrupt system files, but after rebooting nothing has changed

The "Restart" option for Security Center is disabled:

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I went more than a week without a solution, but I was due for an upgrade anyway… New hard drive and fresh installation means the problem is gone even though it was never solved.

Unfortunately, I won't be able to test or accept an answer for this problem.

Best Answer

I had the same sort of symptoms. In the Windows Security Center, under Virus and threat protection, it said "Your virus & threat protection is managed by your organization."

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I note you mentioned the Registry Keys under HKLM/SOFTWARE/Microsoft/Windows Defender. Nice spotting, but it seems like there is another key that is causing the problem for some users.

Steps to a solution:

  1. Press the Windows key and type "regedit"
  2. On the regedit icon that appears, right-click and select Run as Administrator.
  3. Navigate to the folder located at HKLM\SOFTWARE\Policies\Microsoft\Windows Defender (You can paste this into the address box at the top of the window, or navigate manually using the side directory structure)
  4. In this folder, there are probably two keys. Right-click and Delete the DisableAntiSpyware key.
  5. Exit regedit, and return to the Windows Defender settings screen (refresh it if necessary). Windows Defender should have the scan options available and working.

Solution adapted from here, with a much more detailed solution here.

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