Windows Defender

Windows Defender (called Windows Security in Windows 10) is an anti-virus program that was first introduced as a downloadable program for Windows XP SP2 before it became bundled with Windows starting with Windows Vista. Initially before Windows 8, it only protected users from spyware. In Windows 8 and later, it also replaced Microsoft Security Essentials when that program merged with Windows Defender transforming it into a full-on anti-virus program.

In Windows 10, the original desktop program was replaced by a UWP app called Windows Defender Antivirus and was bundled with the Windows Defender Security Center app which was added with the Windows 10 Creators Update. It was then renamed to Windows Security Center in Windows 10 October 2018 Update before it was renamed to Microsoft Defender Antivirus in Windows 10 May 2020 Update.