Automatically Install Definition Updates for Windows Defender

One of the benefits of Windows Vista is that it has built in spyware protection with the Windows Defender tool. Defender has frequent updates much like virus scanner products. Frequent updates are good, the annoying thing is that every time there is an update, Windows Update pops up in the task bar and asks you to install the latest update. Because I have Windows Updates set to not install automatically, this requires a few clicks every few days. I always wished there was a way to install the Defender updates automatically.

I finally figured out how to make this happen. It turns out that Defender is scheduled to automatically download updates at 2am every day and then scan your machine. This is great if you keep you machine on 24 hours a day. But I put my machine in hibernate every night to save electricity so the scheduled process rarely gets run. This means that the Defender updates don’t get downloaded automatically causing Windows Update to prompt me to install them.

To fix this just schedule the scan to occur at a time when you are more likely to be using the computer. My computer is usually on in the evening so I set Defender to scan daily at 9pm. This way the updates will get downloaded automatically when the computer is most likely to be on. And I haven’t noticed much of a slowdown of Vista when the scan is running.

Here are details steps on how to enable the automatic definition updates:

  1. Open the Windows Start Menu and type “defender”.
    Launch Defender from the Start menu
  2. Click Windows Defender.
    Click Windows Defender
  3. Click Tools.
    Click on Tools
  4. Click Options.
    Click on Options
  5. Make sure these options are set:
    • Automatically scan my computer is checked.
    • Frequency is set to daily.
    • Approximate time is set to a time that your computer is usually on.
    • Check for updated definitions before scanning is checked.
    • The other options don’t matter so set them however you like.
      Set the Defender options
  6. Close out all the dialogs and you should be all set.


  1. #1 by Howard Feaver on February 19, 2009 - 7:06 am

    I do not like having to install defender every time i run it or am i doing something in correct

  2. #2 by Svein Børge Nygård on April 15, 2009 - 8:20 am

    Thanx :)

  3. #3 by Jesper on June 17, 2009 - 5:16 am

    I haven’t tried your “solution”, but I suppose it works. Thanks for the tip.

    Still, it’s ridiculus that in order to receive the latest definition pattern automatically, you also have to scan your computer! If you know what you’re doing on the net, it’s a complete and utter waste of resources to scan daily. I also do not believe that you can’t tell when the scanning is running. It will affect your computers response times, memory usage a.s.o. But then, when running Vista, slow responses is probably something you get used to.

  4. #4 by Myles on July 2, 2009 - 6:33 am

    I also agree that that is just too much. Microsoft should set up defender to update on its own without Windows Update and requiring the users intervention, if they have Windows update set up that way. Because I don’t want every single update that windows throws at me. But of course I want all the Defender definitions.

  5. #5 by Dave Miller on December 17, 2009 - 10:28 am

    Thanks, I had exactly the same situation you described.

  6. #6 by Tom on May 3, 2010 - 5:48 am

    Me too, thx!

  7. #7 by MK on June 1, 2010 - 10:48 pm

    Same situation here…

  8. #8 by Mike on December 9, 2011 - 6:15 pm

    Add a Scheduled Task to run %ProgramFiles%\Windows Defender\MpCmdRun.exe (might have to replace this with the static path) with -SignatureUpdate in the option. Have this run every day and it will update Windows Defender.

  9. #9 by TerDale on April 19, 2012 - 11:39 pm

    Patrick, thanks for the info. Anyway, dunno about Vista, but on Windows 7, if one looks at Task Scheduler one can see that the option to “run it as soon as possible if missed” is checked by default.
    So, I do think that your changes were successful not because of the scheduled time change, but because you changed “Check for updated definitions before scanning” option, which is unchecked by default.

    Anyway, thanks for the heads up, it allows me to understand this.
    Thanks too to Mike, for the “update without scanning” tip.

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