Windows Defender marking safe apps as malware even after marked as safe

Question

Windows Defender marking safe apps as malware even after marked as safe

Anonymous

Windows Defender, being about as high-quality as I have come to expect from it, has started marking random files from a legitimately purchased and installed Steam game as various types of malware. It varies on what files it takes issue with and what it thinks they are, but no matter how many times I tell it to stop quarantining random files, it refuses to do so.

Even when I fully disable it in favor of my other antivirus, it continues to reactivate itself to quarantine random harmless files. I run it in administrator mode, and I have total permissions on the device, including root permissions, so there is no system or file on the device which can ignore my directions.

Trying to replicate this is difficult, as Defender acts unpredictably at the best of times, and will no longer do it when I try to replicate the issue.

What is the solution here? Is Defender itself the virus, and if so, how do I purge it?

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Answer accepted by question author

quietman7 MVP Alumni 19,830 Volunteer Moderator

Is Defender saying malware or are the detections Potential Unwanted Programs/Apps (PUPs/PUAs)?

If the latter, the most common reason for this is potentially unwanted app blocking is turned on in Reputation-based protection found under Windows Security > App & browser control > Reputation-based protection settings.

If the detections are indicated as malware and you believe Microsoft Defender is detecting a legitimate file as a threat it may just be a false positive, then you should submit the file for malware analysis to Microsoft Research and Response team analysis.

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2 additional answers

Answer 1

quietman7 MVP Alumni 19,830 Volunteer Moderator

Then it most likely is a a false positive detection and you need to follow my previous instructions for submitting the detected files to Microsoft.

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Answer 2

It is marking them as malware. Mostly Trojans, but occasionally other virus types as well. I will try to get photos later if I can get it to start causing problems again.

It always declares them severe and always as comprising various .dll files.

The app has been verified on Steam, as have the files. There is no malware, Defender is wrong.