Windows 10: How reinstall windows defender

So, I might be wrong about this, but this is the conclusion I reached:

- Windows Defender itself might be infected or corrupted


I have Bitdefender as a secondary antivirus and it detects in temp folder Application.Agent.BSO as a potential threat





I get spammed with this notification so decided to investigate further.


I used procmon.exe to look at the access to that specifical temp file.

And the culprit: MsMpEng.exe

Now, unfortunately, I closed procmon.exe and lost the log, but it seems it tried to access a lot of variations of that temp file: from tmp0000008.ink, tmp0000008.exe, tmp0000008.bat, etc


Which is very suspect. It looks like it tries to inject something.



I disabled Windows Defender and got not more access to that suspect temp file. Which means it's 100% MsMpEng.exe the culprit. I wouldn't be on high alert, but I had a recent password leak, which could've been a keylogger. Found nothing though after a thorough search, and it might just be a data hack somewhere were my password got busted, but it made a little paranoid, so I might overreact here.


But, for my peace of mind, I'm looking into reinstalling windows defender to clean slate. Is this possible?

:)

 

Windows Defender problem

Hi Ernst,

To troubleshoot this issue, we suggest that you check the Windows Defender service if it's running. If you are using a third party spyware/malware program, it may disable the Windows Defender service. To do this, please follow the steps below:

• Press Windows + R key.
• Type services.msc.
• Right-click Windows Defender service and click
  Start.

Let us know the result.

 

window defender

• • • 
      You will want to print these instructions for offline reference -
      

IMPORTANT => DON'T SKIP ANY STEP perform all Steps in one uninterrupted session - If a Step says to reboot
reboot.

Problems starting Windows Defender in Windows 8/8.1/10

Pləase let us know what fixes the problem or if the pяoblem remains.

• • • 
      `~`
      

 

Good alternative to Windows Defender on 8.1

I had to do a format and reinstall on my main rig, and thought I may as well upgrade to 8.1. My only real gripe is my Downloads folder lagging like hell, which I've read is due to Windows Defender. Now I really like MSE/Windows Defender because it's unobtrusive and lets me do what I want to do without pissing me off. Several attempts to try another antivirus program have always resulted in me going back to MSE (either due to viral infection or general annoyance). The lagging, while not an issue per se, is annoying the hell out of me. So I'd like suggestions for a good, free alternative that will be unobtrusive, not try to block everything I want to do (I'm smart enough to know what I'm doing), and not make my PC lag even when running a schedules scan.

Thanks.