Windows 8 and 8.1 Forums

Windows Defender

  1. #1


    Posts : 511
    Windows 10 Pro 64 bit

    Windows Defender


    Why does Windows Defender want to scan my PC so often? I have it scheduled to scan daily at about 2:30 AM. Sometimes after about 4 hours it says I need to scan.

      My System SpecsSystem Spec

  2. #2


    Posts : 1,360
    Windows 8.1 Enterprise


    Windows Defender will usually do a quick scan after it has updated the definition file. Microsoft typically sends out updates about twice everyday.

    Also, sometimes Windows Defender will get stuck trying to delete it's older definition files. If you manually run maintenance from the Action Center it will perform several tasks. First, it will optimize the database for faster scanning. Then, it will delete older cached definitions files. Next, it will run a full scan of the system. Finally, it will run an integrity check on Windows Defender components. Manually running maintenance is a good idea every so often.

    The other scenario is Windows Defender has detected malware that it's not able to remove. If this is the case a notification should pop up saying "Detected Potentially Harmful Software".
      My System SpecsSystem Spec

  3. #3


    One thing I would add, if you are by chance running CCleaner, make sure to uncheck the following items in the Applications Tab:

    Windows Defender
    MS AntiMalware

    These are the log files & if they are erased, Defender assumes it hasn't run a scan in a while.
      My System SpecsSystem Spec

  4. #4


    Posts : 511
    Windows 10 Pro 64 bit


    I do have auto maintenance turned on. No problem there. It Hasnítdetected any threats. I am using CCleaner ver 4.09. I donít have MS Antimalware listed. I unchecked Windows Defender. I excluded C:\Windows\Temp\MpSigstub.log and C:\Windows \Windowsupdate.log from CCleaner and rebooted. Next day needs to scan again. Ithink I have found the problem. I excluded C:\Temp\MpCmdRun.log from CCleanerand it hasnít done it in 2 days. Thanks for the help ecthch and Brog 386. I'll give it a couple more days, then mark it solved.
      My System SpecsSystem Spec

  5. #5


    Posts : 511
    Windows 10 Pro 64 bit


    Still working OK. I think excluding C:\Temp\MpCmdRun.log from CCleaner was the fix.
      My System SpecsSystem Spec

  6. #6


    Good deal, glad you got it sorted & good find on the additional items to block
      My System SpecsSystem Spec

  7. #7


    Good info, thanks for following up!!
      My System SpecsSystem Spec

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