Microsoft Defender Missing After Disabling Security

To restore Microsoft Defender and the Windows Security app on your Windows 10 system, you can follow these steps:

1. Check Group Policy Settings: If you have Group Policy settings that disable Microsoft Defender, you will need to remove or change those settings. You can do this by running gpedit.msc and navigating to Computer Configuration > Administrative Templates > Windows Components > Microsoft Defender Antivirus. Ensure that the policy "Turn off Microsoft Defender Antivirus" is set to Not Configured or Disabled.
2. Registry Check: You can also check the registry to ensure that Microsoft Defender is not disabled. Open the Registry Editor (regedit) and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender. Look for a value named DisableAntiVirus and ensure it is set to 0. If it does not exist, you may need to create it and set it to 0.
3. Re-enable Microsoft Defender: You can run the following PowerShell command as an administrator to re-enable Microsoft Defender:

      & "${env:ProgramFiles}\Windows Defender\MpCmdRun.exe" -WdEnable
   

4. Update Security Intelligence: After re-enabling, update the security intelligence by running:

      & "${env:ProgramFiles}\Windows Defender\MpCmdRun.exe" -SignatureUpdate -MMPC
   

5. Restart Your Computer: After performing the above steps, restart your computer to ensure changes take effect.

If you continue to experience issues, consider checking for any third-party antivirus software that might be conflicting with Microsoft Defender, as it may automatically disable Defender.

References:

• Troubleshoot Microsoft Defender Antivirus service startup problems
• Troubleshoot Microsoft Defender Antivirus while migrating from a non-Microsoft solution