Microsoft Security Essentials uses Microsoft Update to check for, and download definition updates every 24 hours. If you have a number of computers in your home or office without (or having limited) internet access, you may have to install the definition updates offline. To download the Microsoft Security Essentials virus and spyware definition update file, click the appropriate link below:

Detailed information about this is available in Microsoft article How to manually download the latest definition updates for MSE.

Alternate Method

If one of your PCs having internet access has already updated itself with the latest definitions for the day, you can obtain the definitions from that system and use it in other systems that share the same architecture (x86 to x86, x64 to x64.)

Locating the Definition Updates Folder in the Source PC

1. Open the following folder path using Windows Explorer, by typing the following in Address Bar:

Windows XP

%Allusersprofile%\Application Data\Microsoft\Microsoft Antimalware\Definition Updates

Windows 7 and Windows Vista

%Allusersprofile%\Microsoft\Microsoft Antimalware\Definition Updates

2. Double-click the {GUID} folder.

Note: {GUID} is a string whose valid format is {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} where X is a hex digit (0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F). For example, the {GUID} string format might look like {A3EB313F-F9D9-442B-A191-2BA607752323}. The {GUID} string varies for each computer.

3. Copy the following files to a removable media.

File nameDescription (via Stuff n Things)
Mpasbase.vdmLast base signature set of AntiSpyware definitions
Mpasdlta.vdmLast delta signature set of AntiSpyware defintions
Mpavbase.vdmLast base signature set of AntiVirus definitions
Mpavdlta.vdmLast delta signature set of AntiVirus definitions again
Mpengine.dllThe AV Engine

Transferring Definition Updates to another PC

Important: Before copying the definition updates to the target computer, disconnect from the internet, and then turn off Microsoft Antimalware Service via Services MMC. To disable Microsoft Antimalware Service, use these steps:

1. Press the WinKey + R keys to bring up the Run command.

2. Type Services.msc, and press {ENTER}

3. Right-click Microsoft Antimalware Service and click Stop

4. Minimize the Services MMC.

5. Open the following folder path using Windows Explorer:

Windows XP

%Allusersprofile%\Application Data\Microsoft\Microsoft Antimalware\Definition Updates

Windows 7 and Windows Vista

%Allusersprofile%\Microsoft\Microsoft Antimalware\Definition Updates

6. Double-click the {GUID} folder.

7. Copy the definition updates from the removable media to this folder.

8. Maximize the Services MMC

9. Right-click Microsoft Antimalware Service and click Start

10. Open Microsoft Security Essentials user interface, and click the Update tab to verify if the definitions are successfully updated.


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9 Comments

  1. daniel
    said this on Thursday, April 3rd 2014 6:47 pm

    Thank you so much. That helped me a lot! :-)

  2. John Dangerbrooks
    said this on Wednesday, June 19th 2013 5:12 am

    Hi. An update: It is no longer necessary (or possible) to stop Microsoft Antimalware Service. Just copy everything in:
    C:\ProgramData\Microsoft\Windows Defender\Definition Updates\{*}

    Into:
    C:\ProgramData\Microsoft\Windows Defender\Definition Updates\Updates

    Then do the most important this: Wait! Within a couple of seconds, MSE or Defender will detect the contents, verifies their integrity, moves them to appropriate {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} folders and turns green.

    Here is PowerShell script for grabbing the updates and storing them in “C:\MSE VD\Handoff”. (Run with admin privileges):
    New-Item “C:\MSE VD”
    New-Item “C:\MSE VD\Handoff”
    Remove-Item “C:\MSE VD\Handoff\*”
    Get-ChildItem “C:\ProgramData\Microsoft\Microsoft Antimalware\Definition Updates\`{*`}” | foreach {
    $sourcePath1=$_.FullName
    $sourcePath1=$sourcePath1+”`\`*”
    Write-Host “Copying” $sourcePath1
    Copy-Item -Path $sourcePath1 -Destination C:\MSE VD\Handoff\”
    }

    And here is the script for the target computer:
    move “C:\MSE VD\Handoff\*.*” “C:\ProgramData\Microsoft\Windows Defender\Definition Updates\Updates”

  3. said this on Saturday, March 23rd 2013 1:45 am

    terrible instructions. Is technical writing even taught anymore???

  4. Mahfuz Hasan
    said this on Wednesday, March 6th 2013 5:47 pm

    Thank you, really appreciate your help. May peace be upon you.

  5. Pramod
    said this on Wednesday, August 31st 2011 1:57 am

    There is no GUID folder in the destination computer as it has never been updated :(
    How do I get the correct guid ?

  6. pawmeas
    said this on Monday, October 25th 2010 5:40 pm

    that alternate update tip is a life saver. thanks a lot man.

  7. R.N.Mehrotra
    said this on Saturday, July 10th 2010 7:44 pm

    Despite all efforts, Microsoft Security Essentials is not getting updated. Every time error appears-’Failed 2 update’.
    Please suggest solution.
    With due regards,
    Mehrotra

  8. Ronald
    said this on Sunday, November 29th 2009 11:32 pm

    **@John Dangerbrooks**
    That sounds like a great idea. Would you mind coming back here to let us know how it turns out.

  9. John Dangerbrooks
    said this on Sunday, November 29th 2009 1:30 pm

    Thank you. That was a great post.

    Still, I’m surprised to see no MSE definition update on Windows Update user interface. Perhaps the reason is that Microsoft does not make the updates available through WSUS. (Mind you, doing so costs a lot of bandwidth for Microsoft)

    But perhaps I can write a Windows PowerShell script or a C# application that automatically disconnect from Internet, disable Antimalware, copy updates, reactivate both and then distribute the updates over the network…?

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