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How to Fix Windows Security Shows Unknown Error on Windows 11: Step-by-Step Solutions

Windows Security is an essential feature in Windows 11 that helps protect your device from viruses, malware, and other threats. Sometimes, you might see an “Unknown Error” message when trying to access Windows Security. This can be frustrating because it stops you from managing your security settings.

Fortunately, this error can often be fixed with a few simple steps. Whether you are a beginner or familiar with Windows, this guide will walk you through easy and effective solutions to resolve the problem.

By following these instructions carefully, you can get Windows Security working smoothly again and keep your computer safe. Let’s dive into the step-by-step solutions.

Each step includes explanations to help you understand why it’s necessary and how it can help fix the error.

Quick Note: Before You Begin

Before trying any fixes, please check the following:

  • Make sure your Windows 11 is up to date. Sometimes updates fix bugs automatically.
  • Restart your computer. A simple reboot can clear temporary glitches causing the error.
  • Ensure you are logged in with an administrator account because some fixes require admin rights.
  • Disconnect any external security software temporarily as it might interfere with Windows Security.

Step 1: Run the Windows Security Troubleshooter

Windows has a built-in troubleshooter that can detect and fix common problems with security features.

  1. Click on the Start button and select Settings.
  2. Go to System > Troubleshoot > Other troubleshooters.
  3. Find Windows Security or Windows Defender in the list.
  4. Click Run next to it and wait for the process to complete.

This step helps identify any issues that Windows can fix automatically, saving you time.

Step 2: Restart Windows Security Service

Windows Security depends on specific services running in the background. Restarting these services can fix errors.

  1. Press Windows + R to open the Run dialog box.
  2. Type services.msc and press Enter.
  3. In the Services window, scroll down and locate Windows Security Service or Security Center.
  4. Right-click it and select Restart. If the service is stopped, click Start.

Restarting the service clears temporary service errors and refreshes the connection Windows Security needs to operate.

Step 3: Check for Corrupted System Files Using SFC Scan

Sometimes, corrupted system files cause Windows Security to malfunction. You can repair these files using the System File Checker (SFC).

  1. Click the Start button, type cmd.
  2. Right-click Command Prompt and select Run as administrator.
  3. In the black window, type the following command and press Enter:
sfc /scannow

This scan can take some time. It will automatically find and fix corrupted system files that might be causing the error.

Step 4: Reset Windows Security App

If the previous steps do not work, resetting the Windows Security app can help. This clears the app’s cache and settings without affecting your personal files.

  1. Go to Settings > Apps > Installed apps.
  2. Find Windows Security in the list.
  3. Click on the three dots next to it and select Advanced options.
  4. Scroll down and click Reset. Confirm if prompted.

This action reinstalls the app and solves issues related to corrupted app data.

Step 5: Update Windows Defender Antivirus Definitions Manually

Windows Defender uses virus definitions to detect threats. Outdated or corrupted definitions can cause errors.

  1. Open Windows Security (if possible) or open Settings > Privacy & Security > Windows Security.
  2. Click on Virus & threat protection.
  3. Under Virus & threat protection updates, click Check for updates.
  4. Wait for the updates to download and install.

Updating definitions ensures your security software can properly scan and protect your system.

Alternative Method: Use PowerShell to Re-register Windows Security

If resetting the app doesn’t fix the problem, you can try re-registering Windows Security using PowerShell. This reinstalls and re-registers the app components.

  1. Press Windows + X and select Windows Terminal (Admin).
  2. In the terminal window, type the following command and press Enter:
Get-AppxPackage Microsoft.SecHealthUI -AllUsers | Reset-AppxPackage

Wait for the process to finish, then restart your computer. This method helps fix deeper app issues.

FAQs

Why does Windows Security show an unknown error?

It can happen due to corrupted system files, stopped services, outdated virus definitions, or app-related issues.

Is it safe to reset the Windows Security app?

Yes, resetting only clears the app’s cache and settings; it does not delete your files or affect Windows functionality.

Can third-party antivirus software cause this error?

Yes, some third-party antivirus programs can conflict with Windows Security, causing errors or disabling features.

Will updating Windows fix the error?

Sometimes, yes. Microsoft regularly releases updates that fix bugs and improve system stability.

What if I cannot open the Command Prompt as administrator?

You need an administrator account to run some commands. Try logging in with an admin account or ask your system administrator for help.

When Nothing Works

If none of the above solutions fix the unknown error, you have a few final options:

  • Use System Restore to revert your computer to a point before the error appeared.
  • Run DISM (Deployment Image Servicing and Management) tool to fix Windows image corruption by entering DISM /Online /Cleanup-Image /RestoreHealth in an admin Command Prompt.
  • Consider contacting Microsoft Support or visiting the official Windows Security Help page.
  • As a last resort, you can perform a Windows 11 reset or clean installation, but make sure to back up your data first.

Conclusion

Windows Security showing an unknown error on Windows 11 can be annoying, but it is usually fixable with simple troubleshooting steps. Starting from running the troubleshooter to resetting the app covers most common causes.

Remember to keep your system updated and regularly check your security settings. If you encounter this error, follow the steps in this guide carefully, and you will likely restore Windows Security without hassle.

Taking these actions helps ensure your PC stays protected and runs smoothly with Windows 11’s built-in security features.

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