How to Cancel an Ongoing Defender Scan started with Start-MpScan

The PowerShell cmdlet Start-MpScan starts a Microsoft Defender antivirus scan, but PowerShell offers no option to stop an ongoing scan. You may wonder how to cancel an ongoing quick/full scan started with Start-MpScan.

Unfortunately, when you start a scan using PowerShell, the Windows Security dashboard doesn’t indicate whether a scan is in progress, and offers no option to cancel a scan.

Also, when you press Ctrl + C in an attempt to cancel the scan, only the notification is removed. But the ongoing scan doesn’t stop.

Resolution

To stop an ongoing scan initiated by the Start-MpScan PowerShell command, use the MpCmdRun.exe console tool.

Open an admin Command Prompt window.

(Note: The following command may not work in PowerShell. Please run it from admin Command Prompt only.)

Run the following command:

"C:\Program Files\Windows Defender\MpCmdRun.exe" -Scan -Cancel

or

"C:\Program Files\Windows Defender\MpCmdRun.exe" -Scan -ScanType -Cancel

You should see the following output:

Argument -cancel detected. Trying to cancel any quick/full scan in progress...
Scan cancelled successfully.

If no scans are ongoing, the command outputs the following message instead:

Argument -cancel detected. Trying to cancel any quick/full scan in progress...
No on-going quick or full scan found.

The above method works irrespective of the method used to start the scan — e.g., via PowerShell, Windows Security dashboard, or the MpCmdRun.exe console tool.

I hope that information helps.