Microsoft defender has stopped working , why?

Question

Error message pops up when I try to open Microsoft defender. I tap on continue but it still will not open.

Answer 1

There can be several reasons why Microsoft Defender has stopped working and is not opening. Here are some potential causes and troubleshooting steps you can take:

1. Service Issues: The Microsoft Defender Antivirus service may have stopped. You can check the status of the service by running the following command in an elevated PowerShell window:

      Get-Service WinDefend | Format-Table -Auto DisplayName, Name, StartType, Status
   

   Ensure that the service is set to Automatic and is currently running.
2. Third-Party Antivirus Conflicts: If you have a non-Microsoft antivirus program installed, it may conflict with Microsoft Defender. Uninstall any third-party antivirus software and restart your computer.
3. Corrupted Definitions or Engine: Corrupted security intelligence or engine files can cause issues. You can remove these by running the following command in an elevated Command Prompt:

      for /f "delims=" %d in ('dir "%ProgramData%\Microsoft\Windows Defender\Platform" /ad /b /o:-n') do if not defined _done "%ProgramData%\Microsoft\Windows Defender\Platform\%d\MpCmdRun.exe" -RemoveDefinitions -All
   

4. Windows Updates: Ensure your system is up to date with the latest Windows updates, as these can include important fixes for Microsoft Defender.
5. Event Logs: Check the event logs for any error codes related to Microsoft Defender. For example, Event ID 5008 indicates that the antimalware engine encountered an error and failed. You can look up the error code for more specific troubleshooting steps.

If the issue persists after trying these steps, consider reaching out to Microsoft Support for further assistance.

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References:

• Troubleshoot Microsoft Defender Antivirus service startup problems
• Review event logs and error codes to troubleshoot issues with Microsoft Defender Antivirus