FIX: Windows Defender Threat Service has stopped. Restart it now (Solved)

Last updated on October 4th, 2020

On a Windows 10-based computer, the Defender Antivirus Security Center may encounter the error: "Threat Service has stopped. Restart it now." The easy way to fix the problem, is to press the "Restart now" button to start the threat service, but in some cases this doesn't work and you receive a new error message that says "Unexpected error, Sorry, we ran into a problem. Please try again."


Windows Defender Threat Service has stopped. Restart it now

This tutorial contains instructions to fix the following problem in Windows 10 Defender Virus & threat protection status: "Threat Service has stopped. Restart it now."

How to FIX: Threat Service has stopped. Restart it now, in Windows 10.

Method 1. Uninstall Third-party Antivirus.

First of all ensure that you haven't installed any other third-party antivirus on your machine, because when you install a third party antivirus in Windows 10, the Windows Defender security is disabled automatically, and the "Threat Service has stopped. Restart it now" error in Windows Security center is just an informational message..

Method 2. Check your system for viruses.

Important: The next step to resolve the Defender error "Threat Service has stopped. Restart it now" in Windows 10, is to make sure that your computer is 100% clean from harmful programs like rootkits, malware or viruses. To accomplish this task, follow the steps from this Quick Malware Scan and Removal Guide. If, after ensuring that your PC is virus free and the threat service is unable to start, continue to the methods below.

Method 3. Modify the Registry Policy for the Windows Defender.

1. Open Registry Editor. To do that:

1. Simultaneously press the Win image + R keys to open the run command box.
2. Type regedit and press Enter to open Registry Editor.


2. Navigate to this key at left pane:

  • HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender

3. Now look at the right pane if you can see a DWORD value named: DisableAntiSpyware

A. If you find the 'DisableAntiSpyware DWORD then double click on it and change its value data from 1 to 0


B. If you don't find the "DisableAntiSpyware' DWORD value, then:

1. Right-click at an empty space on the right pane, and from the menu that appears, choose: New > DWORD (32-bit) Value.


2. Name the new value: DisableAntiSpyware and press Enter.


4. Close Registry Editor.
5. Restart your computer.

Method 4. Enable the Windows Defender Antivirus Service in Registry.

1. Open Registry Editor.
2. Navigate to this key at left pane:

  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinDefend

3. At the right pane, modify the Start REG_DWORD value, from 4 to 2


4. Close registry editor and restart your computer. *

* Note: If you cannot modify the Start value, with error: "Cannot Edit Start: Error writing the value's contents", then try to modify the registry in Safe Mode and if you fail again, continue to the next method.


Method 5. Enable the Windows Defender Antivirus Service in Registry OFFLINE

Step 1. Create a System Restore Point. *

* Note: This step is optional, but, for precautionary reasons I suggest to create a restore point of your system current state in order to restore your PC if something goes wrong.

To Create a restore point:

1. Open Windows Explorer.
2. At the left pane, right-click on "This PC" icon and select Properties.
3. Click System Protection.
4. At System Protection settings, click Configure.


5. At Restore Settings window:

a. Check the Turn on system protection.
b. Adjust the maximum disk space used for system protection, to (about) 10-15% of the maximum disk space.
c. Click OK.

Enable system protection windows 10

6. Now click Create to create a restore point of the current state.


7. Type a recognizable name for the restore point and click Create.
When the operation is completed, continue to step-2.

Step 2. Modify the 'WinDefend' registry key Offline.

1. Proceed and start Windows 10 in recovery mode. To do that use one of the following ways:

A. From Windows GUI: Right click on Start menu and then press the Restart button while pressing the SHIFT key on your keyboard.

B. From Windows Sign-in screen: Click on the Power button and then choose Restart while pressing the SHIFT key on your keyboard.

Start Windows 10 in Recovery Mode

2. At Recovery options, go to Troubleshoot -> Advanced Options -> Command Prompt. (Your computer will restart)
3. After restart, select an account with administrative privileges, type the password (if any) and click Continue.
4. In command prompt window type regedit and press Enter.


5. In Registry Editor, highlight the HKEY_LOCAL_MACHINE key.


6. From File menu, select Load Hive.


7. At 'Look in' select the disk where Windows are installed on (commonly is listed as disk "D:").


8. Now navigate to the following path on the OS disk:

  • Windows\system32\config\

9. Highlight the SYSTEM file and click Open.


10. Type a Key Name for the offline registry database (e.g. "Offline") and press OK.


11. Now navigate at the following registry key:

  • HKEY_LOCAL_MACHINE\Offline\SYSTEM\ControlSet001\Services\WinDefend

12. At the right pane, modify the Start REG_DWORD value, from 4 to 2 and click OK.


13. When done, highlight the key you previously created (e.g. the "Offline" key ) and from the File menu, choose Unload Hive to write back the changes you made to the Registry.


14. Select Yes when asked to unload the current key,


15. Close the 'Registry Editor' and the 'Command Prompt' windows.
16. Click Turn off your PC.


17. Power On you PC and boot to Windows normally.

Method 6. FIX Windows Problems with DISM & SFC tools.

1. Open command prompt as administrator. To do that:

1. In the Search box type: cmd or command prompt
2. Right click on the command prompt (result) and select Run as Administrator.

command prompt administrator

2. At the command prompt window, type the following command & press Enter:

  • Dism.exe /Online /Cleanup-Image /Restorehealth

dism restore health windows 10 8 7

3. Be patient until DISM repairs the component store. When the operation is completed, (you should be informed that the component store corruption was repaired), give this command and press Enter:


sfc scannow windows 10-8

4. When SFC scan is completed, restart your computer.

Method 7. Repair Windows 10 with an in-place Upgrade.

Another method that usually works, to fix Windows problems, is to perform a Windows 10 Repair-Upgrade, by using the Media Creation tool to create an ISO or USB Windows 10 install media. For that task follow the detailed instructions on this article: How to repair Windows 10.

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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