Windows 11 Windows Defender not working is a common problem. If you cannot use it to protect your PC against viruses and malware attacks, some troubles may come to you. What should you do to fix Windows 11 Security not working to get real-time protection? Refer to this post and MiniTool will show you some possible methods.

Windows Defender (Microsoft Defender Antivirus) is built into Windows to protect your computer from viruses and malware.

However, you may sometimes find that Windows Defender is not working, Windows Security won’t open, or virus protection features are unavailable.

This guide explains why Windows 10/11 Windows Defender not working and how to fix it with proven solutions.

Quick Answer: Why Is Windows Defender Not Working?

Windows Defender is integrated into Windows 11/10 and doesn’t need a separate download. If it stops working, it’s often due to third-party antivirus programs, disabled services, corrupted files, outdated components, or wrong settings.

Fix it by removing conflicting antivirus software, restarting services, updating Windows, running SFC and DISM scans, resetting Windows Security, or checking settings.

What Is Windows Defender and Where to Find It in Windows 11?

Windows Defender, or Microsoft Defender Antivirus, is the built-in antivirus protection in Windows 11, so there’s no need to download it separately.

To open Windows Security in Windows 11:

  1. Press Win + I to open Settings.
  2. Go to Privacy & security > Windows Security.
  3. Click Open Windows Security.

open Windows Security Windows 11

From Windows Security, you can manage virus protection, run malware scans, check security settings, and troubleshoot Microsoft Defender problems.

How to Fix Windows Defender Not Working in Windows 11/10?

Fix 1. Check for Third-Party Antivirus Conflicts

A common reason Windows Defender stops working is the presence of another antivirus program, which can lead Windows to disable Microsoft Defender to avoid conflicts.

Try these steps:

  1. Open Settings.
  2. Go to Apps > Installed apps.
  3. Find your antivirus software.
  4. Uninstall it if you no longer need it.
  5. Restart your computer.

Then open Windows Security again and check whether Windows Defender works.

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Fix 2. Restart Security Center Service

Windows Defender relies on various Windows services. If these services are stopped or disabled, Windows Security may not function properly.

Follow these steps:

Step 1: To get the Run dialog, press Win + R.

Step 2: Type services.msc into the textbox and click OK to open Services.

Step 3: Go to find the Security Center service from the right pane, right-click it and choose Restart.

Besides, you should also check these services – Windows Defender Advanced Threat Protection, Windows Defender Firewall, Windows Defender Antivirus Network Inspection Service, and Windows Defender Antivirus Service and make sure they are running.

restart Security Center service

Step 4: Double-click each service to open the Properties window and set the Startup type to Automatic.

After that, go to check if Windows Defender can work. If it is still not working as normal, try other methods below.

Fix 3. Set Date and Time Correctly

A common reason why Windows Defender won’t start/work is an incorrect time and date since most system features depend on time and date. So, make sure your date and time are set correctly.

Step 1: Click the Start icon from the Taskbar in Windows 11 and choose Settings to open this app.

Step 2: Move to the Time & language tab on the left side and click Date & time in the right pane.

Step 3: Click the Change button to set the correct time and date.

change time and date in Windows 11

 
Tip: In addition, you can set date and time in other methods, and here is a related article – [3 Ways] How to Change Date and Time & Sleep Time on Windows 11.

Fix 4. Update Windows to the Latest Version

Sometimes Windows Defender Windows 11 missing or Windows 11 Security not working appears due to the bugs in the certain Windows versions. To fix it, you can update it to the latest version to see if the issue is resolved.

Step 1: Click Start > Settings to get Windows 11 Settings interface.

Step 2: Go to Windows Update in the left sidebar and click Check for updates.

Step 3: If the system checks for some available updates, download and install them on your Windows 11 PC. Then, you may be able to run Windows Defender for PC protection against viruses and threats.

download and install Windows 11 updates

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Fix 5. Run SFC and DISM

Corrupted system files can disrupt Windows Defender. Use the System File Checker (SFC) and DISM tools to repair Windows.

Step 1. Run SFC Scan.

Open Command Prompt as administrator and run sfc /scannow.

Wait until the scan finishes. If SFC repairs corrupted files, restart your PC and check Windows Defender.

Step 2. Run DISM If SFC Fails

If SFC cannot fix the issue, run:

DISM /Online /Cleanup-Image /RestoreHealth

Wait until the process completes.

Step 3. Run SFC Again.

After DISM finishes, run sfc /scannow again to verify that Windows system files are repaired.

Fix 6. Check Group Policy Settings

Group Policy settings can disable Microsoft Defender, especially on Windows Pro and Enterprise editions.

Follow these steps:

Step 1: Open Run, type: gpedit.msc, and press Enter.

Step 2: Go to Computer Configuration > Administrative Templates > Windows Components > Microsoft Defender Antivirus.

Step 3: Make sure Defender is not disabled.

Restart your PC and check Windows Security.

Fix 7. Reset Windows Security App

If Windows Security does not open or shows errors, resetting the app may solve the problem.

  1. Open Settings.
  2. Go to: Apps > Installed apps.
  3. Find Windows Security.
  4. Click Advanced options.
  5. Select Reset.

reset Windows Security

Restart Windows and open Windows Security again.

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Fxi 8. Perform a Clean Boot

The running third-party services and programs may interrupt Windows, leading to Windows 11 Windows Defender not working. To get rid of the trouble, you can try to perform a clean boot.

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Step 1: Open the Run window by pressing Win + R, type msconfig, and click OK.

Step 2: Under the Services tab, tick the checkbox of Hide all Microsoft Services.

hide all Microsoft services

Step 3: After that, click Disable all to disable all the services except Microsoft services.

Step 4: Go to the Startup tab and click Open Task Manager.

Step 5: Choose programs individually and click Disable to disable them to fix Windows Security not working in Windows 11.

Fix 9. Make Changes in Your Registry

If Windows Defender won’t start or work after trying many solutions, you can try to change Registry settings. Before you do, you had better back up your registry keys in Windows 11 to avoid system corruption due to mistaken operations.

Step 1: Type regedit to the search box and click Registry Editor.

Step 2: Go to this path: Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender.

Step 3: Locate DisableAntiSpyware in the right pane. If it is not here, right-click Windows Defender and choose New > DWORD (32-bit) Value to create it.

Step 4: Double-click this key and set its value data to 0.

disable antispyware registry

Fix 10. Reset This PC

If all of these methods cannot fix Windows 11 Windows Defender not working, the last solution you can try is to reset your PC to its factory settings. To do this task, go to Settings > System > Recovery > Recovery options > Reset this PC. Then, choose an option based on your need and finish the resetting operation by following the instructions on the screen.

To know more information about PC resetting or reinstallation, refer to this post – How to Reinstall Windows 11? Try 3 Simple Ways Here Now!

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“Is Windows Defender not working in Windows 11 or Windows 11 Security not working? Try these solutions to fix it. Or, you can share them with your friends on Twitter.”Click to tweet

Suggestion: Back up Your PC

After trying the methods above, you should run Windows Security properly to protect your PC from malicious programs, viruses, and some other threats. In practice, only running antivirus is not enough to keep your PC safe. From this post – Is Windows Defender Enough? More Solutions to Protect PC, you know the reasons.

To prevent your PC’s data loss due to malware and virus attacks, you can choose to make a full backup for them. Besides, you had better create a system image to avoid system breakdown due to virus infection.

Well then, how can you back up your computer in Windows 11? A professional PC backup software should be your good assistant. Here, we strongly recommend using MiniTool ShadowMaker.

This backup software is compatible with Windows 11/10/8/7 and can be used to back up your files, folders, disks, partitions, and Windows systems. In addition, you can use it to clone a hard drive to another disk for disk upgrade or the entire disk backup. Besides, data sync is also supported. Importantly, you can use it to only create backups for the changed or newly added data without taking much disk space.

Now, get MiniTool ShadowMaker by clicking the following download button and install it on your Windows 11 PC for backup.

MiniTool ShadowMaker TrialClick to Download100%Clean & Safe

Step 1: Double-click the icon of this software to launch it.

Step 2: Click Backup and you can see this software backs up the system by default. To create a system image, you can directly go to choose a destination path to continue. If you need to back up files, click Source to go to choose files you need.

Step 3: After selecting backup source and destination, click Back up Now to execute the backup task immediately.

back up Windows 11

 
Tip: In addition to using MiniTool ShadowMaker to back up your PC in Windows 11, you can try other ways. Just refer to this post – How to Back up Windows 11 (Focuses on Files & System) to know more.

How to Prevent Windows Defender from Not Working Again

To ensure Windows Defender functions effectively:

  • Keep Windows updated regularly.
  • Avoid using multiple antivirus solutions simultaneously.
  • Do not disable Windows Security features.
  • Download software only from reputable sources.
  • Perform regular malware scans.

Windows 11 Windows Defender Not Working FAQ

Is Windows Defender the same as Windows Security?
No, they aren't exactly the same. Windows Security is the overall management dashboard, while Windows Defender (Microsoft Defender Antivirus) is the specific antivirus program within it. Think of Windows Security as the control center and Windows Defender as the security guard.
Why is my Virus & threat protection not working?
Your “Virus & Threat Protection” may not be working properly due to conflicts with third-party antivirus software, disabled core Windows services, or corrupted system files. Additionally, malware can intentionally block these features.
Why is Windows Defender service missing?
The Windows Defender service may be missing due to aggressive malware deleting or hiding it, a corrupted registry from third-party antivirus uninstallation, severe system file corruption, or an incomplete Windows update.
How do I know if Windows Defender is running?
To check if Windows Defender is running, look for the shield icon in the system tray at the bottom right. A green checkmark indicates it's active.
You can also verify this by going to Settings > Update & Security > Windows Security and checking the “Virus & threat protection” status.

Final Thoughts

Windows Defender issues are often due to antivirus conflicts, disabled services, or corrupted files. Start by checking antivirus software and restarting Windows Security services. For persistent problems, consider using SFC, DISM, or Group Policy troubleshooting.

To safeguard your system, it’s also a good idea to back up your PC with MiniTool ShadowMaker. For help, leave a comment or email [email protected].

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About The Author

Charlotte
Charlotte

Position: Columnist

Charlotte is a technology columnist with a strong focus on the Windows operating system, specializing in disk management, backup, and data recovery. She is passionate about analyzing computer errors, identifying root causes, and delivering practical solutions. In her free time, she stays updated on the latest developments in computer systems and hardware while continuously learning new technologies to broaden her expertise. Her writing style is clear and easy to understand, making complex technical topics accessible even to users with limited computer knowledge.

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