Windows Defender Ends prematurally

Question

Good Afternoon, I am currently on Windows 10 1809

I ran manually Windows Defender yesterday evening (Quick Scan) all was well, scanned approx. 13,000 files took about 7-8 mins.

This morning Logged on and Manually updated the definitions on Defender and tried to run a quick can...…..took 40 Seconds and would finish at only 6 Files !

So I thought I'd do a Full Scan and same happened 6 Files, 40 Seconds (40 Seconds is a long time to do 6 files anyway).

I tried running it in a Command Prompt Screen (Admin) MpCmdRun.exe from Platform : 

C:\ProgramData\Microsoft\Windows Defender\Platform\4.18.1908.7-0       Outcome the same as above.

So used and old platform without updating definitions : C:\ProgramData\Microsoft\Windows Defender\Platform\4.18.1908.5-0  Outcome the same as above.

I have updated the Definitions  twice since then and no change in outcome.

I went into  Safe Mode with Command Line to run Microsoft Support Emergency Response Tool (Had just updated the Definitions  about 10 minutes before) FULL SCAN (/F) and the same thing happened it scanned 6 files and just finished normally as Defender above.

I then downloaded McFee "Stinger" & then rang it in safe mode on the command line and ran normally.

I then tried running Microsoft Windows Malicious Software Removal Tool (KB890830) in same situation and ran normally to completion scanning over, 1,300,000 files, finished normally. HOWEVER the definitions in this go back to Patch Tuesday in August (July I think definitions done).

So is there an issue with the latest definitions  for Defender and Microsoft Support Emergency Response Tool ?

or something else ?

Kindest Regards & Thanks,

Paul

Answer 1

Hi Smeed:

   "The issue seems to be partially fixed."

Partially?  Both quick and full scans seem to be working correctly on all our Windows 10 and 8.1 PCs.

Answer 2

The issue seems to be partially fixed since virus definition (Security intelligence update) version 1.301.1684.0

Updated info here: https://borncity.com/win/2019/09/18/scan-issues-with-msd-defender-antimalware-version-4-18-1908-7/

Latest security intelligence updates for Windows Defender Antivirus and other Microsoft antimalware

Answer 3

You're not alone.

Quite a few users on Windows 7, 8.1 and 10 are reporting the same.

Microsoft has to fix it...

Doing a custom scan should still work.... 

Some articles (some in German, you could use Translate or another translator to  read them)...

• https://www.askwoody.com/forums/topic/ms-security-essentials-stops-scanning-after-29-files/
• https://www.deskmodder.de/blog/2019/09/18/windows-defender-aktuell-mit-einem-scan-problem-durch-die-antimalware-version-4-18-1908-7/
• https://www.borncity.com/blog/2019/09/18/scan-probleme-mit-defender-antimalware-version-4-18-1908-7/
• https://www.askwoody.com/2019/microsoft-tries-to-fix-the-sfc-scannow-bug-introduced-by-a-patch-in-july-ends-up-clobbering-defender-malware/

Answer 4

Hi Paul:

     A neighbor of mine called me with the same problem you have and after running several other malware programs to see  if his PC was infected,  it didn't cure the problem.  So,  I  went home  and checked and both my Windows 10 PCs have the same problem.  I then checked with another neigbor and his PC was also failing to complete a full or quick scan.   All these PCs are on Windows 10 v1903.  I have 2 other PCs running Windows 8.1 with Media Center and Windows Defender scans are working fine.

    Apparently Microsoft has sent us another faulty update,  since we know at least 4 different computer owners have the same problem!  Hopefully Microsoft is aware of the problem and will send us an update to fix the faulty update soon!

Answer 5

Hi Paul

This is a widely reported bug in the latest Defender update over the last 36 hours, Microsoft have reported they are aware of this bug and will push out a patch for this as soon as they have worked out the underlying issue . ..