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This detection is for potentially unwanted modifications (PUMs) in the Windows registry where specific file types and processes are excluded for scanning by Windows Defender and Microsoft Security Essentials. Such changes may have been set by malware to avoid detection.

System modifications

Suspect registry values are created under the following keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender\ Exclusions\Processes

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender\ Exclusions\Extensions

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft Antimalware\ Exclusions\Processes

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft Antimalware\ Exclusions\Extensions


Malwarebytes can change the value data to 0 so the exclusions will be inactive, without user interaction.

Also, we advise users to do a full system scan as PUM.Optional.MSExclusion could have been added to the system by malware or a PUP.

Add an exclusion

When a Potentially Unwanted Modification (PUM) is detected on your computer, Malwarebytes for Windows does not know whether it was authorized. Optimization software, malware, and Potentially Unwanted Programs (PUPs) are known to make these types of changes, hence they are regarded as potentially unwanted by design. To have Malwarebytes for Windows ignore a PUM, you must add the PUM to the Allow list. Here’s how to do it.

  1. When a PUM appears in the list of Scan results.
  2. Uncheck the entry or entries related to the PUM.
  3. Then click on Next.
  4. You will see a prompt giving you several options.
  5. Choosing Always ignore will add the PUM to the Allow List.
  6. You can remove them there when you decide they should no longer be ignored.
  7. When the PUM is on the Allow list it will no longer show up in your Scan results.