Windows Defender Antivirus scans failing after few secs in Windows 10

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    Windows Defender Antivirus scans failing after few secs in Windows 10

    Windows Defender Antivirus scans failing after few secs in Windows 10


    Posted: 18 Sep 2019

    There's currently a major bug in Windows Defender, the free antivirus software that ships with Windows 10.

    Running a Quick or Full scan will fail after a few seconds and only go through a handful of files, resulting in incomplete, superficial results. Such scans are usually known to take tens of minutes, and even hours.

    The issue has been widely reported over the past two days on the Microsoft tech support forums [1, 2, 3, 4, 5], Reddit [1, 2, 3, 4], and tech support sites like AskWoody, DeskModder, BornCity, and Bleeping Computer.

    The bug impacts Windows Defender version 4.18.1908.7 and later, released earlier this week. The bug was introduced while Microsoft tried to fix another bug introduced with the July 2019 Patch Tuesday...

    ...Fortunately, there's a way around this bug, if users need to perform daily scans of sensitive systems. Instead of relying on a Quick or Full scan, users can use the Windows Defender "Custom scan" feature and select the drives of folders they'd like scanned, manually, one by one.


    Read more: https://www.zdnet.com/article/window...a-few-seconds/


    How to Manually Scan Files, Folders, and Drives with Windows Defender Antivirus in Windows 10

    Brink's Avatar Posted By: Brink
    18 Sep 2019


  1. Posts : 25,011
    10 Home x64 (21H2) (10 Pro on 2nd pc)
       #1



    The article is misleading in stating that...

    The bug impacts Windows Defender version 4.18.1908.7 and later, released earlier this week. The bug was introduced while Microsoft tried to fix another bug introduced with the July 2019 Patch Tuesday...

    The bug affects ALL Microsoft's scan engines in ALL supported OS, that's Defender and Microsoft Security Essentials in Windows 7, Windows 8.x and Windows 10. It appears that the virus definitions are the cause of this bug. The bug is in ANY Microsoft AV that uses a virus definition from about 1.301.1600.0 or newer.


    Here I demonstrate the same bug in Windows 7 using MSE.


    Bree said:
    ... 'before and after' Quick Scan test on a different W7/MSE machine.

    Windows Defender Antivirus scans failing after few secs in Windows 10-image.pngWindows Defender Antivirus scans failing after few secs in Windows 10-image.png

    A subsequent Full Scan on this machine also only checked 50 items.
    Windows 10 Defender - Quick/Full Scans Last Only 15 Seconds??
      My Computers


  2. Posts : 1,561
    Windows 10 Home 20H2 64-bit
       #2

    Does this affect automatic checks?
      My Computer


  3. Posts : 25,011
    10 Home x64 (21H2) (10 Pro on 2nd pc)
       #3

    Faith said:
    Does this affect automatic checks?
    Yes. The bug affects the Quick scan and the Full scan. The automatic scan is a Quick scan. Only the Custom scan works normally.

    It appears that the real-time protection is still working normally though.
      My Computers


  4. Posts : 3,245
    Windows 10 and windows insider
       #4

    Bree said:
    Yes. The bug affects the Quick scan and the Full scan. The automatic scan is a Quick scan. Only the Custom scan works normally.

    It appears that the real-time protection is still working normally though.
    Thank you Bree. At least some comfort knowing real-time protection appears to be working.
      My Computer


  5. Posts : 25,011
    10 Home x64 (21H2) (10 Pro on 2nd pc)
       #5

    magilla said:
    Thank you Bree. At least some comfort knowing real-time protection appears to be working.
    Yes, I have confirmed that with the EICAR test virus.
      My Computers


  6. Posts : 118
    Windows 10 Pro
       #6

    Bree said:
    Yes, I have confirmed that with the EICAR test virus.
    Ah awesome. I was worried about that too. Thanks for confirming real time protection is working as usual, Bree.
      My Computers


  7. Posts : 61
    win 10
       #7

    I also tried using the off-line scan , and I believe that wasn't working correctly either.
      My Computers


  8. Posts : 834
    Windows 10 Pro 64bit 21H2 19044.1766
       #8

    Bree said:
    It appears that the virus definitions are the cause of this bug. The bug is in ANY Microsoft AV that uses a virus definition from about 1.301.1600.0 or newer.
    In support of Bree and his Defender Definition as the cause of this bug you can run the new definitions against the old platform which is in a different version folder:

    "C:/ProgramData/Microsoft/Windows Defender/Platform/4.18.1907.4-0/\MpCmdRun.exe" Scan -ScheduleJob -ScanType 1

    Same 10 second run as

    "C:/ProgramData/Microsoft/Windows Defender/Platform/4.18.1908.7-0/\MpCmdRun.exe" Scan -ScheduleJob -ScanType 1

    Code:
    ------------------------------------------------------------------------------------
    MpCmdRun: Command Line: "C:\ProgramData\Microsoft\Windows Defender\platform\4.18.1908.7-0\MpCmdRun.exe" Scan -ScheduleJob -ScanType 1
     Start Time: ‎Wed ‎Sep ‎18 ‎2019 15:07:56
    
    MpEnsureProcessMitigationPolicy: hr = 0x1
    Starting RunCommandScan.
    Scanning path as file: (null).
    Start: MpScan(MP_FEATURE_SUPPORTED, dwOptions=16385, Timeout in days = 1)
    MpScan() started
    Time Info - ‎Wed ‎Sep ‎18 ‎2019 15:08:07 MpScan() was completed
    Finish: MpScanStart(MP_FEATURE_SUPPORTED, dwOptions=16385)
    Finish: MpScan(MP_FEATURE_SUPPORTED, dwOptions=16385, Timeout in days = 1)
    MpScan() has detected 0 threats.
    MpCmdRun: End Time: ‎Wed ‎Sep ‎18 ‎2019 15:08:07
    -------------------------------------------------------------------------------------
    
    
    -------------------------------------------------------------------------------------
    MpCmdRun: Command Line: "C:\ProgramData\Microsoft\Windows Defender\platform\4.18.1907.4-0\MpCmdRun.exe" Scan -ScheduleJob -ScanType 1
     Start Time: ‎Wed ‎Sep ‎18 ‎2019 15:10:03
    
    MpEnsureProcessMitigationPolicy: hr = 0x1
    Starting RunCommandScan.
    Scanning path as file: (null).
    Start: MpScan(MP_FEATURE_SUPPORTED, dwOptions=16385, Timeout in days = 1)
    MpScan() started
    MpScan() was completed
    Finish: MpScanStart(MP_FEATURE_SUPPORTED, dwOptions=16385)
    Finish: MpScan(MP_FEATURE_SUPPORTED, dwOptions=16385, Timeout in days = 1)
    MpScan() has detected 0 threats.
    MpCmdRun: End Time: ‎Wed ‎Sep ‎18 ‎2019 15:10:13
    -------------------------------------------------------------------------------------
      My Computers


  9. Posts : 56,100
    Multi-boot Windows 10/11 - RTM, RP, Beta, and Insider
       #9

    Just received a new definition update, and quick scan appears to be normal, I think.

    Windows Defender Antivirus scans failing after few secs in Windows 10-2019-09-18_18h32_55.pngWindows Defender Antivirus scans failing after few secs in Windows 10-2019-09-18_18h32_00.png
      My Computers


 

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