Windows spent three weeks saying your antivirus was off. It wasn't.

Since late August, Windows has been telling people their antivirus was switched off when it was not. That has now stopped.

The notification read "Microsoft Defender Antivirus is turned off". It appeared when the PC started and then again at odd intervals, and it kept appearing even for people who had gone into settings and turned notifications off. Open Windows Security to check and everything looked normal: real-time protection on, definitions current, nothing to do. Microsoft logged the problem on its release health dashboard on 28 August and marked it resolved on 17 September. The fix arrived as Microsoft Defender Antivirus update version 4.18.26080.4. The bug reached everything from Windows 10 version 22H2 up to Windows 11 26H1, plus every supported version of Windows Server.

You do not have to chase it. Defender updates itself separately from the monthly Windows patches, often several times a day, so most machines will have picked this one up already. If the message is still turning up, open Settings, go to Windows Update, check for updates and restart.

It is worth saying why a false alarm is more than an annoyance. "Your antivirus is turned off" is the exact line tech support scammers put in their pop-ups, because it frightens people into picking up the phone. Three weeks of Windows crying wolf is three weeks of everyone learning to click past security warnings. Tendvane's health score reads the real protection state out of Windows rather than trusting the notification, which is one way to settle the question if you were unsure whose word to take.