Microsoft Security Essentials includes a command-line utility which can be used to update the virus/malware definitions, initiate a scan, undo a recent definition update and perform other tasks. To know how to use the command-line utility, open a Command Prompt window (CMD.EXE) and execute the following command:

"%ProgramFiles%\Microsoft Security Essentials\MpCmdRun.exe" /?

-? / -hDisplays all available options for this tool.
-Trace [-Grouping #] [-Level #]Starts diagnostic tracing
-RemoveDefinitions [-All]Restores the installed signature definitions to a previous backup copy or to the original default set of signatures
-RestoreDefaultsResets the registry values for Microsoft Antimalware Service settings to known good defaults
-SignatureUpdate [-UNC]Checks for new definition updates
-Scan [-ScanType]Scans for malicious software
-Restore -Name <name> [-All]Restore the most recently or all quarantined item(s) based on name
-GetFilesCollects support information

In addition to the above information, detailed information for each command-line parameter is shown when you run the above command.

To update the MSE virus/malware definitions, use this command:

"%ProgramFiles%\Microsoft Security Essentials\MpCmdRun.exe" -SignatureUpdate

The command-line tool can be useful if you want to update MSE using Batch file, Script or using Task Scheduler.

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  1. marc
    said this on Friday, August 31st 2012 4:40 pm


    @color F3
    @timeout /t 40
    @echo off
    “C:\Program Files\Microsoft Security Client\MpCmdRun.exe” -SignatureUpdate -MMPC
    @timeout /t 10


  2. Dave
    said this on Wednesday, March 23rd 2011 9:29 pm

    C:\Program Files\Microsoft Security Client\Antimalware>MpCmdRun.exe -scan -ScanT
    ype 0

  3. Trevor Lahey
    said this on Thursday, December 9th 2010 9:40 am

    Because it’s supposed to be like this:

    START msseces.exe -Scan -0


  4. Capoderra
    said this on Tuesday, September 28th 2010 11:15 pm

    I was able to update the virus definitions with the following code:
    cd “%ProgramFiles%\Microsoft Security Essentials\”
    MpCmdRun.exe -SignatureUpdate

    But unable to start a scan with the following code in the same batch file:
    START msseces.exe -Scan -ScanType 0

    what gives?

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