Windows 10: Windows Defender - Threat found but can't resolve

Hi,Windows Defender reported a threat Wacatac.H!ml in a CrystalDiskMark tmp file: I selected to remove the file. I also took the precaution of uninstalling CrystalDiskMark and formatting full format, not quick format the G: drive where it was found an external SSD.Windows Defender still reports the threat as present in this file even though the drive is no longer connected i.e. there is no G: drive attached to the computer but the above message still pops up when I do a virus scan. The date and time of the alert is 10:17am a few hours ago now. Assuming I've done everything to get rid

:)

 

Windows defender false positive - forced to allow threat

Windows defender has started to identify C:\Windows\System32\mshta.exe as a threat [normally reported as a Trojan Powessere.G]. I use mshta.exe to run an hta custom MsgBox - I have been hoping to keep using my current CustomMsgBox tool [batch file calling a vbs-hta file] until later this year when I hope to have had enough time to replace it with a PowerShell alternative.

Windows defender's notification lets me "allow the threat" but that seems to me to be a bigger security hole than is necessary - it will now ignore a potentially real intrusion when all I want to run is a genuine Windows component. My immediate problem is fixed but I would prefer to fix the false positive using the exclusions list.

I cleared the 'Allowed threats history' so I could use the exclusions list instead. I added C:\Windows\System32\mshta.exe to the file exclusions list and I checked that it had taken properly by checking the exclusions list both in the UI & in the Registry. But the exclusion made no difference, it continued to detect and block the exe.

I have repeated the attempt several times [by clearing the allowed threats list & exclusions list beforehand] and the results are the same every time
- allowing the threat works,
- using the exclusions list has no effect.

I studied the relevant tutorial but have not spotted an error in what I have been doing - Add or Remove Windows Defender Exclusions

Does anybody with experience of using the exclusions list to counter false positives have any suggestions for me?

Denis

 

Threats detected by Windows Defender

If you really want to be sure if those threats are removed completely then I would suggest to clean install Windows. That’s the only way to know for sure.

And always disconnect from the internet next time you encounter malware. That’s the first step to take, especially if you have more than one computer sharing the same network.

 

Windows Defender/Security - no option to "Allow" potential threats?

If you want to control what does defender do to threats you can do it trough GPO in the following location:

Computer configuration\Administrative templates\Windows components\Microsoft defender antivirus\Threats
Here configure option:
Specify threats upon which default action should not be taken when detected

Threats are categorized by level, you assign default action per threat level.

EDIT:
Btw. to open GPO (Local Group Policy) follow these steps:

1. click on start button
2. type: gpedit.msc
3. right click on gpedit.msc and run as Administrator