Windows Defender The threat service has stopped

Have you tried restarting your PC?

Do you have any other Anti-Virus software installed?

Some users might be experiencing a glitch with starting the Threat Service (Windows Defender Antimalware Service) that was delivered on Patch Tuesday. So the first thing to try would be manually restarting the PC lots of times, with a break between the restarts (Start button > Power > Restart), as suggested by Le Boule in this thread:

https://answers.microsoft.com/en-us/protect/forum/protect_defender-protect_scanning-windows_10/windows-defender-virus-threat-protection-restart/9215a1e1-d386-477b-b22f-d608365b255a

This issue might also be related to the known glitch where the Security Center Service needs to be restarted in order to get Windows Defender up and running – so try this:

• Manually restart the Security Center, and then attempt to start the Windows Defender Antivirus Service:

1.  Press Win Key + R

2.  Type “services.msc” and click OK.

3.  Right-click on Security Center and click Restart

4.  Right-click on Windows Defender Antivirus Service and click Start.

Other suggestions for starting Windows Defender are presented in this Forum Article:

https://answers.microsoft.com/en-us/protect/forum/protect_defender-protect_start/problems-starting-windows-defender-in-windows/808253bb-db89-4db9-a4e5-1c91a86489e9

I hadn’t noticed that PrashantKumar96 actually advised setting DisableAntiSpyware = 0 **** in his forum article. Before you do that, you should always try just deleting any possible entry for DisableAntiSpyware = 1, since that setting might have been added by another program or by malware – and that setting will always prevent Windows Defender from starting. For the sake of both ease and safety, this should be done with a REG command.

Type “cmd” in the search box; and then right-click on Command Prompt and select Run as administrator.

And then copy, paste, and enter this command:

REG DELETE "HKLM\SOFTWARE\Policies\Microsoft\Windows Defender" /v DisableAntiSpyware 

This is the proper way to enable Windows Defender when it's been turned off via Group Policy.

We can see that there’s a general confusion with respect to this Group Policy setting by the way that Brink equates deleting the DisableAntiSpyware entry with setting its value to 0.

DisableAntiSpyware DWORD

(delete) or 0 = On

1 = Off

https://www.tenforums.com/tutorials/5918-turn-off-windows-defender-windows-10-a.html

But this setting actually uses a three-state logic, where the absence of the setting specifies the normal Automatic Disabled compatibility mode for Windows Defender. Setting DisableAntiSpyware = 0 sets Windows Defender's operational state to “always on” [DisableAntiSpyware = 0 (logical “no/never”)], whereas [DisableAntiSpyware = 1 (logical “yes/always”)] sets Defender’s operational state to “always off”; and where removing the DisableAntispyware registry entry simply returns Defender to its default operational state – where Defender will be automatically disabled by the installation of any third-party AV app, and automatically enabled when a third-party AV app is uninstalled.

Windows Defender operational states

Truth Value of DisableAntiSpyware      Operational State

Undefined (unspecified)                       Automatic Disabled (default)

True (1, logical yes/always)                  Always Off

False (0, logical no/never)                    Always On     

Therefore, setting DisableAntiSpyware = 0 should only be done as a last resort, after first deleting any DisableAntiSpyware entry, and after all of the following troubleshooting steps have been fully applied, since having to resort to this “always on” setting means that there’s something seriously wrong with the system; and because this setting will have adverse and unforeseen consequences. For example, I set Defender to “always on” after installing Avast Free in order to see what effect this would have – and although I didn’t see any prompt to restart the Defender Service in the WDSC app itself, the prompt did immediately appear in the Windows Defender Antivirus UI, and this turned on Windows Defender (complete with real-time protection) after just a moment's hesitation.

So we need to be clear that setting DisableAntiSpyware = 0****will allow Windows Defender to run alongside any third-party AV app with its real-time protection enabled, which would result in all kinds of different performance and operational issues in the event that a third-party AV app was installed at some future point in time. So this setting is something to be avoided if at all possible, and you should always try the REG DELETE command provided above first, and then follow these troubleshooting steps before setting Windows Defender to "always on":

• Remove any undetected malware by scanning with several third-party malware-removal apps, starting with Malwarebytes Free:

https://answers.microsoft.com/en-us/protect/forum/protect_other-protect_scanning-windows_other/list-of-malware-removal-tools/d824b9af-ebd8-4c47-94e2-8ee6c544c100

• Run the cleanup tools for any previously installed or preinstalled AV apps:

https://answers.microsoft.com/en-us/protect/forum/protect_other-protect_start-windows_other/list-of-anti-malware-product-removal-tools/2bcb53f7-7ab4-4ef9-ab3a-6aebfa322f75

• Run the standard Windows 10 system integrity checks:

https://answers.microsoft.com/en-us/windows/forum/windows_10-update/system-file-check-sfc-scan-and-repair-system-files/bc609315-da1f-4775-812c-695b60477a93

If none of these steps allow you to restart the Windows Defender Antivirus Service, then you can try setting the Group Policy for Widows Defender to “always on”.

Type “cmd” in the search box; and then right-click on Command Prompt and select Run as administrator.

And then copy, paste, and enter this command:

REG ADD "HKLM\SOFTWARE\Policies\Microsoft\Windows Defender" /v DisableAntiSpyware /t REG_DWORD /d 0 /f

Then click the Restart button (it might be necessary to restart the PC first).

If this REG ADD command fails to resolve the issue, then run the REG DELETE command above to delete the Disable Antispyware entry, and then temporarily install a free third-party AV solution to tide you over until we can get a handle on things. Replacing Defender with a third-party AV app should at least provide you with a viable alternative for Defender’s real-time protection, and allow you to connect to the internet safely:

https://www.pcmag.com/article2/0,2817,2388652,00.asp

GreginMich

thank you so much for your help, but unfortunately i tried all the steps but the problem is still exist ! i can't turn it on

Alright, an update:

1. I ended up giving up on fixing the problem, and completely reformatted and reinstalled Windows 10.
2. After about 6 hours, I now have all of my apps and data restored, and the 2018-05 cumulative update has been installed also. I'm on 10.0.17134.
3. So far, the Defender service is working and hasn't crashed.

So for the poor soul who has the same issue, finds this thread, and is looking for an easy solution, I hope you managed to solve this with less hassle than I did.

yes i did but nothing changed, i had malwarebytes but i uninstall it completely and the problem still exist !