how do I reinstall windows defender for windows 10

Hi Lucy,

Welcome to Microsoft community.

• How did you uninstall Windows Defender?

Please follow the below steps and check:

 Step 1: Enable Windows defender from control panel 

1.    Press Windows + X, Click on control panel.

2.    On right top corner click on View and then choose large items.

3.    Now from the list click on Windows Defender and try to enable it. 

If not try to enable it from services. 

Step 2: Enable Windows defender from services.msc. 

1.    Press Windows + R, to open run prompt.

2.    Type services.msc and press enter to open services list.

3.    Under services look from Windows defender service and start the service.

If you face any issue while troubleshooting, please provide the outcome, so that we can work on your issue. 

Hope the information helps, if you have any further queries, feel free to post. We are here to assist you.

Rehards,

Guru Kiran

Error 577: window can not verify the digital signature for this file. A recent hardware or software change might have installed a file that is incorrectly or damaged, or that might be malicious software from an unknown source

it didn't work for me in services.msc I got error 1068

I accidently uninstalled Windows Defender for Windows 10. How do I reinstall it?

[Moved from Windows]

Me too.

I accidently uninstalled Windows Defender for Windows 10. How do I reinstall it?

[Moved from Windows]

The Windows 10 update process resulted in Windows Defender being turned Off and I cannot manage to turn it on again. I simply get the message "This app has been turned off and isn't monitoring your computer. If you're using another app to check for malicious or unwanted software, use Security and Maintenance to check that app's status." But I am not using anything else... When I go to Security & Maintenance and try to turn on Defender's "Spyware and unwanted software protection" and "Virus protection" the operation simply fails each time - at first it appears to Turn On but then defaults back to OFF.