In Windows 11 (and earlier Windows Versions), Microsoft has provided a basic antivirus product in Windows Defender. While it works, and Microsoft does a good job of keeping it updated, Defender misses some viruses when tested.
So get a commercial antivirus product instead. Upon installation of a commercial antivirus, Windows Defender will turn itself off.
If you’re using any earlier versions of Windows; Windows 8, 8.1, 7, Vista or XP, then DEFINITELY get a commercial antivirus product, NOW.
Check out an independent review of antivirus products from AVTest – The Independent IT-Security Institute.
Link – AVTest – The Independent IT-Security Institute