It looks like the Windows Defender in Windows 8 won't upgrade the signatures automatically, if Windows Update is set to "Notify, but don't install the upgrades".

Is my impression real? Is there is a fix?

I don't like automatic updates as I don't want to install useless updates like the ballot screen or something else, I want to choose.

  • 1
    If you don't like auto-updates, and you think Defender is waiting for you to OK the updates, then what "Fix" are you looking for? Nov 4, 2012 at 17:52
  • 2
    @techie007 I don't like software auto-updates because I don't like the system suddenly saying I have to reboot. Updating malware signature files is another matter. Nov 4, 2012 at 18:01
  • @IsaacRabinovitch So you're suggesting that you (and the OP as well?) want Defender to update automatically, but not Windows Updates? Nov 4, 2012 at 18:05
  • I'd like to have the virus signatures have the autoupdate, but having a manual control on the system updates Nov 4, 2012 at 18:40

5 Answers 5


Since Defender updates are delivered with Windows Updates, then just like other Windows Updates, if you have it set to Notify Only, it will wait until you OK it.

From the Windows 8 Help and Support regarding Defender:

To help keep your definitions up to date, Windows Defender works with Windows Update to automatically install new definitions as they're released. You can also have Windows Defender check online for updated definitions before scanning.

According to that, you can also have Defender do an (extra) check for definitions before starting a scan but. There is no UI control for that available, but you can easily modify how the scheduled scan is launched and with what options Windows Defender is working. The system calls MpCmdRun.exe, which has quite some command line flags. Here is how you modify it to update the signatures before the scheduled scan:

  1. Open the Scheduled Tasks UI and search in the library for Microsoft\Windows Defender.

  2. Change the command line flags (for the task MP Scheduled Scan) to:

    SignatureUpdate Scan -ScheduleJob -WinTask -RestrictPrivilegesScan

  3. Done. Now Windows Defender will update it's signatures before it does a scan.

  • Sure, and so can the Defender in Windows 8 if you hit "Update" within Defender, and I'm pretty sure that's how it was in Win7 as well? Nov 4, 2012 at 18:24
  • @IsaacRabinovitch: Your screenshot shows MSE, not Defender. MSE was a separate product and not part of Windows, whereas Defender was included in Win7 by default. MSE's features have now been rolled into Defender, and so a separate install isn't required any more on Win8.
    – Karan
    Nov 4, 2012 at 19:56
  • @Karan My bad. The fact that MS provides two separate malware solutions is confusing.¶According to Wikipedia, the version of Defender that comes with 8 provides the same protections as SE. This suggests that a good way to get non-WU signature updates is to replace Defender with SE. Nov 4, 2012 at 20:27
  • @IsaacRabinovitch: Except you can't do that any more. AFAIK MSE cannot be installed in Win8 to replace Defender, as was possible in Win7. If you know of a hack or get it to work reliably/stably, it would be nice if you can share in a separate thread.
    – Karan
    Nov 4, 2012 at 20:28
  • @IsaacRabinovitch - MSE isn't supported on Windows 8 and cannot be installed on Windows 8. You can replace defender with any other product except MSE.
    – Ramhound
    Nov 26, 2012 at 15:56

Nope, Windows defender gets its virus signatures via Windows Update. If you read this Microsoft documentation you will see they make mention to updates taking place via WSUS (this is just a corporate front end for Windows Updates).

  • 2
    I link to a source would be nice.
    – Synetech
    Nov 4, 2012 at 18:26
  • How it works, if you explain or give an official link then it seems be good.
    – avirk
    Nov 4, 2012 at 18:40

I don't want Windows to update automatically, so I created an old time batch file to update Windows Defender, without updating Windows.

https://docs.google.com/open?id=0B_SFfC0m5rI0TE16NXB3a0doLVk (bat file)

You can put it in: C:\Users-your username-\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup Or just click to run it.


This is pretty stupid to tie in updates for the OS to the updates for the security software (when the former happens once a month and the latter one -- once a day.) But, we're dealing with Microsoft ...

I couldn't seem to find an easy way to make Windows Defender auto-update itself on my Windows 8.1, so I came up with this solution:

  1. Go to Control Panel -> (Switch to classic view) -> Administrative Tools -> Task Scheduler.

  2. Set up a recurring daily task to run the following command (with double-quotes):

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

with the following arguments:


I personally set it to run at 9 AM daily, but you can pick your own time.

PS. I know, Microsoft Task Scheduler is an obtuse creature that needs a long tutorial of its own, but the good thing is that you have to deal with it only once.


One fix is to bookmark this page and download the latest definitions for defender and install them manually on a regular basis.

Someone could possibly script this download and install procedure and set it as a task to run regularly, beyond my skills though.

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