FIX: Windows Security Not Working in Windows 11.
In this article, you'll learn what might be preventing Windows Defender from starting, and then we'll show you step-by-step how to fix the problem: Windows Defender Security not working.
Windows Defender (aka 'Windows Security'), the built-in antivirus software in Windows 10/11, is crucial for protecting your computer from malware and other online threats. However, there are several factors that can prevent Windows Defender to not start, leaving your system vulnerable.
What can cause Windows security not working problem?
- Conflicting third-party antivirus software: Installing another antivirus program may affect the operation of Windows Defender. In some cases, even if you have uninstalled third-party antivirus programs, the remaining registry entries may still cause Windows Defender to not start.
- Corrupted system files: Damaged or missing system files can disrupt Windows Defender's functionality.
- Registry or Group Policy modifications: Incorrect registry or group policy changes made by the user or by a malicious program can disable Windows Defender.
How to FIX: Windows Defender Security won’t open on Windows 11/10.
If the Windows Security (aka "Windows Defender") does not start in Windows 10/11, follow these steps in order to fix the problem.
- Uninstall Third-Party Antivirus.
- Scan for Malware and Viruses.
- Perform a Clean Boot.
- Start or Restart the Security Center service.
- Repair Windows System Files.
- Reset Windows Defender from PowerShell.
- Enable Windows Defender in Registry.
- Enable Windows Defender in Group Policy.
- Repair Windows 10/11.
Method 1. Uninstall Third-Party Antivirus.
One of the main reasons that Windows Defender Security cannot start is an installed third-party antivirus program. So, if you have installed a third-party security program, uninstall it, restart your PC and check if the problem remain. *
* Note: Even if you haven't installed a security software yourself, your computer may have it pre-installed. To see if this is happening:
1. Type "control panel" in the search and then open the Control Panel app and go to Programs > Uninstall a program.
2. Next, look for any installed third-party antivirus and if there is one, select it and click Uninstall.
3. When uninstall is completed, restart your PC and check if the problem remain. *
* Important: Restart your computer even if you haven't uninstalled any programs. Sometimes Windows Defender-related services may be stuck and not working, but restarting the computer can force them to work properly.
Method 2. Scan for Malware/Viruses.
Before proceeding further, ensure that your computer is clean from viruses and malware. To accomplish this task you can use this Malware Scan and Removal Guide to check and remove viruses or/and malicious programs that may be running on your computer.
After scanning and cleaning your computer for malware, check if the problem persists. If not, you're done here, otherwise continue to the next step.
Method 3. Perform a Clean Boot.
Sometimes, other applications running in the background can conflict with Windows Defender and prevent it from running. To find out if this is causing the Windows Defender startup problem, start your computer with all third-party services disabled by doing a clean boot using these steps:
Step 1. Disable Startup programs.
1. Press CTRL + SHIFT + ESC to open Task Manager.
2. In the Startup tab, disable (one by-one) all the third-party programs running at Windows Startup. Then reboot your PC.
3. After rebooting, check if the problem remains and if so, proceed to Step-2. If not, reopen the Task Manager and enable one by one the disabled programs and reboot until you find the culprit.
Step 2. Disable Third-Party Services.
1. Press the Windows + R keys to open the 'Run' command box.
2. Type msconfig and press Enter to open the System Configuration utility.
3. At Services tab, check the Hide all Microsoft services checkbox.
4. Then press the Disable all button, to disable all non Windows services that start with Windows. When done, click OK and restart your PC.
5. Check if Windows Defender works now. If yes, open 'msconfig' again and enable one by one the disabled services and reboot until you find the culprit. If the problem persists, select the the 'General' tab, choose Normal Startup, reboot your PC and continue to next method.
Method 4. Start or Restart the 'Security Center' service.
To ensure Windows Defender works well, "Security Center" Service should be running.
1. Press the Windows + R keys to open the 'Run' command box.
2. Type services.msc and press Enter to open the Services control panel.
3. Find the Security Center service and check if it running. According the result do the following:
- If "Security Center" service is not running, right-click on it and click Start to start the service.*
- If "Security Center" service is running, right-click on it and click Restart.*
* Note: If the "Start" & "Restart" options are inactive (greyed out), skip to next method.
Method 5. Repair Windows System Files.
Repairing Windows system files is a common but important step in solving Windows 10/11 problems like the one mentioned here.
1. Open Command Prompt as Administrator. To do that, type "cmd" or "command prompt" in the search and then click Run as administrator in Command Prompt result.
2. At the command prompt window, copy-paste the following command & press Enter:
- Dism.exe /Online /Cleanup-Image /Restorehealth
3. Be patient until DISM repairs component store. When the DISM operation is completed, copy-paste the command below and press Enter:
- SFC /SCANNOW
4. When SFC scan is completed, restart your computer and check if the problem is fixed.
Method 6. Fix Windows Defender Not Starting using PowerShell.
1. In Windows Search, type PowerShell and select Run as Administrator to open PowerShell as an Administrator.
2. In PowerShell window, copy and paste the following command and then press Enter.*
- Get-AppxPackage Microsoft.SecHealthUI -AllUsers | Reset-AppxPackage
* Note: If after giving the above command, you receive the error "package not found" or something similar, give this command instead:
- Get-AppXPackage -AllUsers | Foreach {Add-AppxPackage -DisableDevelopmentMode -Register “$($_.InstallLocation)\AppXManifest.xml”}
3. After command execution, close PowerShell, reboot your PC and try again to open Windows Defender.
Method 7. FIX Windows Defender Not Working in Registry.
1. Press the Windows + R keys to open the Run dialog box.
2. Type "regedit" and press Enter to open the Registry Editor.
2. In Registry, navigate to this location:
- HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender
3. At the right pane double-click to open the DisableAntiSpyware REG_DWORD value.*
* Note: If the "DisableAntiSpyware" value doesn't exist, skip to next step or do the following:
- Right-click on empty space, and choose New > DWORD (32-bit) Value.
- Rename the "New Value #1" to "DisableAntiSpyware" and press Enter.
- Continue to next step.
3. Set the Value data to 0 to enable Windows Defender and then press OK.
4. Close the Registry Editor and reboot your PC.
Method 8. Enable Windows Defender in Group Policy.
Sometimes, Windows Defender is disabled because of a group policy that disables it, either set by the user or by malware. *
* Note: This method applies only to Windows 10/11 Professional Editions.
1. Press Windows + R keys to open the Run dialog.
2. Type gpedit.msc and press OK.
2. In the Local Group Policy Editor, navigate to:
- Computer Configuration > Administrative Templates > Windows Components > Microsoft Defender Antivirus.
3a. Double-click to open the Turn off Windows Defender Antivirus policy in the right pane.
4. In the window that appears, choose Not Configured or Disabled and then click Apply and OK.
5. Close the Group Policy Editor and restart your PC.
Method 9. Repair Windows with an In-place Upgrade.
If, after following the methods above, you're still having problems, your last option is to repair Windows with an in-place upgrade. To do this, use the instructions in one of these tutorials, depending on your version of Windows.
- How to Repair Windows 10 with an In-Place Upgrade.
- How to Repair Windows 11 with an In-Place Upgrade.
That's it! Which method worked for you?
Let me know if this guide has helped you by leaving your comment about your experience. Please like and share this guide to help others.
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