Microsoft Defender is described as 'Windows Security (known as Windows Defender Antivirus before Windows 10 May 2020 Update, Windows Defender before Windows 10 Creators Update, or Microsoft Defender Antivirus before Windows 11) is an anti-malware component of Microsoft Windows' and is a very popular Anti-Virus app in the security & privacy category. There are more than 100 alternatives to Microsoft Defender for a variety of platforms, including Windows, Mac, Android, Linux and iPhone apps. The best Microsoft Defender alternative is Malwarebytes Anti-Malware, which is free. Other great apps like Microsoft Defender are Avast Free Antivirus, ClamAV, Bitdefender Antivirus and Spybot - Search & Destroy.