If Windows is telling you that Microsoft Defender Antivirus has been turned off, you can ignore it — the warning is wrong. Microsoft acknowledged this week that a bug in its latest Defender Antivirus update causes the Windows Security app to incorrectly display the message “Microsoft Defender Antivirus is turned off” along with a prompt to “Tap or click to turn on Microsoft Defender Antivirus.” Your antivirus is actually running normally, and all settings should confirm it is active. The false alert appears when Windows starts and can recur intermittently even if you’ve turned off security notifications.
The issue affects all supported Windows client and server versions, including Windows 11 26H1 and Windows Server 2025. Microsoft says it is working on a fix and will release it in a future Defender Antivirus update. In the meantime, the correct action is to leave Defender alone — do not attempt to manually re-enable or reinstall it, as doing so is unnecessary and could create confusion. This follows a pattern of similar false alerts Microsoft has had to address in recent months: in April, it corrected invalid BitLocker and Windows Recovery Environment error codes, and in July 2025, it asked users to disregard erroneous Windows Firewall alerts after a preview update.
How to check if you’re affected
Affected versions are any Windows device running a supported Microsoft Defender Antivirus version after the latest August 2026 Defender update — this includes Windows 11 (all supported builds), Windows 10, and Windows Server products. To confirm your antivirus is actually on, open Windows Security, go to Virus & threat protection, and check that “Real-time protection” shows as On. If it does, the “Antivirus is turned off” notification is a false alarm and no further action is needed.