
The company's acquisition was announced by Microsoft on December 16, 2004. Windows Defender was initially based on GIANT AntiSpyware, formerly developed by GIANT Company Software, Inc. Microsoft AntiSpyware Beta 1 (Version 1.0.701) running on Windows XP In the Windows 10 Anniversary Update, a new logo is introduced and a pop-up notification will appear to announce the results of a scan, even if no viruses are found. In Windows 10, Windows Defender settings are controlled in the Windows Defender Security Center. It also uses the same anti-malware engine and virus definitions from MSE. Protection against viruses was subsequently added in Windows 8 which resembles Microsoft Security Essentials (MSE). Windows Defender featured an integrated support for Microsoft SpyNet that allows users to report to Microsoft what they consider to be spyware, and what applications and device drivers they allow to be installed on their systems. It also has the ability to remove installed ActiveX software. It includes a number of real-time security agents that monitor several common areas of Windows for changes which might have been caused by spyware.

Windows Security (known as Windows Defender Antivirus before Windows Update, Windows Defender before Windows 10 Creators Update, or Microsoft Defender Antivirus before Windows 11) is an anti-malware component of Microsoft Windows.
