Microsoft Defender Bug Triggers False “Antivirus Turned Off” Alerts on Windows

Microsoft confirmed a bug in Microsoft Defender Antivirus that intermittently generates false “Microsoft Defender Antivirus is turned off” notifications on many Windows client and server versions after updates. The issue affects multiple Windows 11, Windows 10 (including LTSC), and Windows Server releases, does not indicate a real service failure or compromise, and Microsoft plans to deliver a fix via a future Defender update; organizations are advised to treat the alerts as notification defects and continue normal verification and incident investigation procedures.