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How to Fix Microsoft Defender Threat Service Has Stopped Error on Windows 11

If you see the “Microsoft Defender Threat Service has stopped” error on your Windows 11 PC, it means the antivirus service is not running properly. This can leave your computer unprotected from threats.

Fixing this error usually involves checking some basic settings and services. You don’t need to be a tech expert to follow these steps.

This guide will walk you through simple and clear solutions to get Microsoft Defender working again.

Take your time and follow each step carefully for the best results.

Quick Note

Before starting, make sure you have:

  • A stable internet connection (some fixes require downloading updates or files).
  • Administrative rights on your computer (you need permission to make system changes).
  • Disabled or uninstalled any third-party antivirus programs temporarily (they can conflict with Defender).

Step 1: Restart Your Computer

Sometimes, a simple restart can fix temporary glitches causing the Defender service to stop.

  1. Click the Start button.
  2. Select the Power icon.
  3. Click Restart.

After your PC restarts, check if Microsoft Defender is running without errors.

Step 2: Check the Microsoft Defender Service

The Defender Threat Service relies on specific Windows services to run. If these services are stopped or disabled, you will see errors.

To check and start the service:

  1. Press Windows + R keys to open the Run dialog.
  2. Type services.msc and press Enter.
  3. In the Services window, scroll down to Microsoft Defender Antivirus Service or Windows Defender Antivirus Service.
  4. Right-click the service and select Properties.
  5. In the Startup type dropdown, choose Automatic.
  6. If the service status is Stopped, click Start.
  7. Click Apply and then OK.

This ensures the Defender service starts every time your computer boots up.

Step 3: Run Windows Security Troubleshooter

Windows has built-in troubleshooters to automatically detect and fix common problems.

  1. Click the Start button and open Settings.
  2. Go to System > Troubleshoot > Other troubleshooters.
  3. Find Windows Security in the list and click Run.
  4. Follow the on-screen instructions to complete the troubleshooting process.

This tool can fix issues related to Microsoft Defender Threat Service automatically.

Step 4: Update Windows 11

Outdated system files can cause Defender to malfunction. Keeping Windows updated ensures bugs are fixed and security features work well.

  1. Open Settings from the Start menu.
  2. Click Windows Update on the left sidebar.
  3. Click Check for updates.
  4. If updates are available, download and install them.
  5. Restart your PC if prompted.

Step 5: Scan for Malware Using Windows Defender Offline

Sometimes, malware can stop Defender services deliberately. Running an offline scan helps remove malware that hides during normal operation.

  1. Open Windows Security from the Start menu.
  2. Click Virus & threat protection.
  3. Under Current threats, click Scan options.
  4. Select Microsoft Defender Offline scan.
  5. Click Scan now and save all work.
  6. Your PC will restart and scan for threats before Windows loads.

Step 6: Reset Microsoft Defender Using PowerShell

If the above steps don’t work, resetting Defender’s components using PowerShell can help fix corrupted files.

Follow these steps carefully:

  1. Type PowerShell in the Start menu search.
  2. Right-click Windows PowerShell and select Run as administrator.
  3. Copy and paste the following command and press Enter:
Get-AppxPackage Microsoft.SecHealthUI -AllUsers | Reset-AppxPackage

This command resets the Microsoft Defender security health package.

After running the command, restart your computer and check if the error is resolved.

Alternative Method: Use System File Checker

Corrupted system files can cause Defender to stop working. The System File Checker (SFC) tool helps repair these files.

  1. Open Windows PowerShell as administrator (see previous step).
  2. Type the following command and press Enter:
sfc /scannow

This scan may take some time. Once completed, it will repair damaged system files automatically.

Restart your PC after the scan finishes.

Frequently Asked Questions (FAQs)

Why does the Microsoft Defender Threat Service stop working?

This can happen due to corrupted system files, malware infections, conflicts with other antivirus software, or disabled Defender services.

Can I use another antivirus with Microsoft Defender?

Windows will usually disable Defender automatically if a third-party antivirus is installed. To avoid conflicts, you should only run one antivirus at a time.

Is it safe to reset Microsoft Defender?

Yes, resetting Defender components using PowerShell is safe and can fix many common issues without harming your system.

Do I need to keep Windows updated for Defender to work?

Yes. Windows updates often include important security patches and fixes that help Defender function properly.

What should I do if the error comes back after fixing it?

It might indicate deeper system issues or malware infection. Running full offline scans and considering professional help may be necessary.

When Nothing Works

If you have tried all the above steps and Microsoft Defender still shows the error, consider the following:

  • Use the Microsoft Safety Scanner: Download this official tool from Microsoft to perform an advanced malware scan.
  • Perform a System Restore: Revert your computer to a previous state before the problem started.
  • Contact Microsoft Support: Visit Microsoft Support for professional help.
  • Reset Windows 11: As a last resort, you can reset Windows while keeping your files, which reinstalls system files and may fix Defender.

Conclusion

The “Microsoft Defender Threat Service has stopped” error can be frustrating, but it is usually fixable with simple steps. Starting with a system restart and checking services often solves the problem.

Running Windows troubleshooters, updating Windows, and scanning for malware help maintain Defender’s health. If necessary, resetting Defender components or repairing system files using PowerShell can fix deeper issues.

Remember to keep your system updated and avoid conflicts with other antivirus programs to prevent future problems. If all else fails, professional support and system restore options remain available.

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