How to Update Microsoft Defender and Run a Quick Scan in One Go

The Windows Defender command-line utility MpCmdRun.exe is prominently used for scheduling scans and updating the signature or definition files. The MpCmdRun.exe command usage info can be obtained by running MpCmdRun.exe with “/?” or without any parameter.

However, it doesn’t mention a useful switch that updates Windows Defender signatures and runs a Quick Scan at once. And this switch is not documented anywhere so far.

MpCmdRun.exe — Signature Update & Quick Scan

To update the definitions and run a Quick Scan in one go, use the switch SignatureUpdateAndQuickScan

"C:\Program Files\Windows Defender\MpCmdRun.exe" /SignatureUpdateAndQuickScan

… and the event (1001) is written to Microsoft-Windows-Windows Defender/Operational event log.

This switch works on Windows 8 and Windows 10.

Generally, if a feature or hidden “switch” in a software program is not documented officially, there is a chance that the manufacturer may have missed updating the help files. However, if you’re someone who doesn’t take anything for granted, you could test such hidden feature on a test computer, just in case.

I’ve used and tested the undocumented SignatureUpdateAndQuickScan in my production computer, and the switch worked exactly as intended without any issues.

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Other MpCmdRun.exe command-line switches

Here are the other commonly used MpCmdRun.exe command-line switches:

Run a Quick Scan

"C:\Program Files\Windows Defender\MpCmdRun.exe" -Scan -ScanType 1

Run a Full Scan

"C:\Program Files\Windows Defender\MpCmdRun.exe" -Scan -ScanType 2

Update the Definitions

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

To see the complete list, open a Command Prompt window and type:

"C:\Program Files\Windows Defender\MpCmdRun.exe"