Windows Defender or Microsoft Defender or Windows Security gets its regular updates through Windows Updates. However if for some reason, the definition update is not able to proceed as expected, then you can try a couple of methods to resolve it. Follow these when you either receive the message that you don’t have the latest definition or updates that cannot be checked, downloaded, or installed.
If Microsoft Defender (Windows Security) in Windows 10 does not update automatically, you can troubleshoot definition update issues, by following these suggestions:
1] Manually check for updates in Windows Defender
2] Run Windows Update Troubleshooter
3] Trigger Microsoft Defender updates using the command line
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