If you have automatic Windows Updates turned off, you may have noticed that you also don’t get Windows Defender updates automatically. There are a lot of reasons why you may want to disable automatic updates. Perhaps you want to pick and choose the ones you accept. Or maybe you don’t want to smash through your data plan limits so you wait until you’re on another network to get your updates. Whatever your reasons are for disabling automatic Windows Updates, not getting up-to-date virus and malware signatures every day is an unfortunate side effect. However, you can force Windows Defender to update its signature file with the following command:
"C:\Program Files\Windows Defender\MpCmdRun.exe" -SignatureUpdate -MMPC
Try it out at a command prompt to see it in action and to verify that it works as advertised. On my computers, I simply created a new task in Task Scheduler that executes the command daily. Now, I can do my Windows Updates manually and receive Windows Defender malware signatures (effectively) automatically.