Open Windows Update settings and look for “ Security Intelligence Update for Microsoft Defender Antivirus — KB2267602.” If it’s missing or stuck, you may need to reset Windows Update.
If the built-in Microsoft Defender Antivirus is not updating automatically, we recommend using the diagnostic and troubleshooting steps outlined in this article to resolve common definition update issues.
Windows 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...