Windows Defender Antivirus scans failing after few secs in Windows 10

f14tomcat said:

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

Same here, what had been 10 seconds a half hour ago now - 1 min 57 sec.

Code:

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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 15:37:42

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 15:39:49 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 15:39:49
-------------------------------------------------------------------------------------

f14tomcat said:

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

Confirmed. The bug is fixed with definitions 1.301.1684.0

Josey Wales said:

Why are there two different versions of Defender

Defender Platform updates create a new version folder under C:/ProgramData/Microsoft/Windows Defender/Platform/

It also re-installs the 4 scheduled tasks under Schedule Task Library / Microsoft / Windows / Windows Defender to include this latest folder path.

This platform folder change took place in December 2017
Microsoft changes Windows Defender Path on Windows 10

The installer will always keep the last working folder under Platform for a month until the next version install cleaning up this oldest 3rd folder within 24 hours.

I'm not sure where your 3.0 Version is coming from?

Just saw this article --

Windows Defender malware scans are failing after a few seconds | ZDNet

Windows broke manual scans with Defender. Tried mine. Broken.

The Pool Man said:

Windows broke manual scans with Defender. Tried mine. Broken.

Check for updates, it was a bad definitions file that broke it, it's fixed with definitions 1.301.1684.0 or higher.

Me too.

That was fast!

(I have to presume someone or someones just got their asses kicked...)

The Pool Man said:

(I have to presume someone or someones just got their asses kicked...)

Took a while to kick the right one - there must have been at least half a dozen new definitions (all broken) issued before they got it right.

Microsoft has now confirmed it was all the fault of the definitions....

Update 9/18/19 7:28 PM: Microsoft has told BleepingComputer that the issue has now been resolved. It turns out it was an issue in the definitions and has been resolved in "Security Intelligence Update for Windows Defender Antivirus - KB2267602 (Version 1.301.1684.0)".

Windows Defender Antivirus Scans Broken After New Update