||This article needs additional citations for verification. (July 2009)|
|A component of Microsoft Windows|
Windows Defender in Windows 8
|Type||Antivirus software on Windows 8; formerly spyware removal software|
|Included with||Windows Vista
|Also available for||Windows XP
Windows Server 2003
|Microsoft Security Essentials|
|Initial release||October 24, 2006|
|Stable release||1.1.1593.0 / May 23, 2007|
|Development status||Deprecated on 10 April 2012|
|Operating system||Windows XP and Windows Server 2003|
|Platform||IA-32 and x86-64|
|Size||4.9 MB – 7.0 MB|
|Available in||22 languages|
|Type||Spyware removal software|
Windows Defender, formerly known as Microsoft AntiSpyware, is a software product that helps combat malware. Windows Defender was initially an antispyware program; it is included with Windows Vista and Windows 7 and is available as a free download for Windows XP and Windows Server 2003. In Windows 8, however, it is upgraded to an antivirus program.
Basic features 
Before Windows 8, Windows Defender featured antispyware capabilities. It included a number of real-time security agents that monitored several common areas of Windows for changes which may be caused by spyware. It also included the ability to easily remove installed ActiveX software. Also 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 system. In Windows 8, functionality has increased to offer antivirus protection as well. Windows Defender in Windows 8 resembles Microsoft Security Essentials and uses the same virus definitions.
Windows Defender is based on GIANT AntiSpyware, which was originally developed by GIANT Company Software, Inc. The company's acquisition was announced by Microsoft on December 16, 2004. While the original GIANT AntiSpyware supported older Windows versions, support for the Windows 9x line of operating systems was later dropped.
The first beta version of Microsoft AntiSpyware was released on January 6, 2005 and was basically a repackaged GIANT AntiSpyware. More builds were released in 2005, with the last Beta 1 refresh released on November 21, 2005.
At the 2005 RSA Security conference, Chief Software Architect and co-founder of Microsoft, Bill Gates, announced that Windows Defender (which was known as Microsoft AntiSpyware prior to November 4, 2005) would be made available free of charge to all validly licensed Windows 2000, Windows XP, and Windows Server 2003 users to help secure their systems against the increasing malware threat.
Windows Defender (Beta 2) was released on February 13, 2006. It featured the program's new name and a significant user interface redesign. The core engine was rewritten in C++, unlike the original GIANT-developed one, which was written in Visual Basic. This improved the application's performance. Also, since beta 2, the program works as a Windows service, unlike earlier releases, which enables the application to protect the computer even when a user is not logged on. Beta 2 also requires Windows Genuine Advantage validation. However, Windows Defender (Beta 2) did not contain some of the tools found in Microsoft AntiSpyware (Beta 1); Microsoft removed the System Inoculation, Secure Shredder and System Explorer tools found in MSAS (Beta 1) as well as the Tracks Eraser tool, which allowed users to easily delete many different types of temporary files related to Internet Explorer 6, including HTTP cookies, web cache, and Windows Media Player playback history. Microsoft later released German and Japanese versions of Windows Defender (Beta 2).
General availability 
Conversion to antivirus 
Windows Defender was released with Windows Vista and Windows 7, serving as their built-in antispyware component. Windows Defender is superseded by Microsoft Security Essentials, an antimalware product from Microsoft which provides protection against a wider range of malware. Upon installation, Microsoft Security Essentials disables Windows Defender and takes over its duty. In Windows 8, Microsoft upgraded Windows Defender into an antivirus program comparable to Microsoft Security Essentials. This new Windows Defender greatly resembles Microsoft Security Essentials and uses the same virus definition updates.
Advanced features 
- Real-time protection
- In the Windows Defender options, the user can configure real-time protection options.
- Internet Explorer integration
- Integration with Internet Explorer enables files to be scanned as they are downloaded to help ensure that one does not accidentally download malicious software. Although it does not integrate with Firefox or other web browsers, Windows Defender still scans downloaded files for malicious code, as part of the real-time protection.
Windows Vista-specific functionality 
Windows Defender had additional functionality in Windows Vista which was removed in subsequent versions of Windows.
- Security agents
- Security agents monitor the computer for malicious activities
- Auto Start - Monitors lists of programs that are allowed to automatically run when the user starts the computer
- System Configuration (settings) - Monitors security-related settings in Windows
- Internet Explorer Add-ons - Monitors programs that automatically run when the user starts Internet Explorer
- Internet Explorer Configurations (settings) - Monitors browser security settings
- Internet Explorer Downloads - Monitors files and programs that are designed to work with Internet Explorer
- Services and Drivers - Monitors services and drivers as they interact with Windows and programs
- Application Execution - Monitors when programs start and any operations they perform while running
- Application Registration - Monitors tools and files in the operating system where programs can register to run at any time
- Windows Add-ons - Monitors add-on programs for Windows
- Software Explorer
- The Advanced Tools section allows users to discover potential vulnerabilities with a series of Software Explorers. They provide views of startup programs, currently running software, network connected applications, and Winsock providers (Winsock LSPs). In each Explorer, every element is rated as either "Known", "Unknown" or "Potentially Unwanted". The first and last categories carry a link to learn more about the particular item, and the second category invites users to submit the program to Microsoft SpyNet for analysis by experts. The Software Explorer feature has been removed from Windows Defender in Windows 7, for which Microsoft recommends using AutoRuns for controlling which programs run when the computer starts.
- Notification of startup programs that run as an administrator
- Windows Defender in Windows Vista automatically blocks all startup items that require administrator privileges to run (this is considered suspicious behavior for a startup item). This automatic blocking is related to the UAC (User Account Control) functionality in Windows Vista, and requires users to manually run each of these startup items each time they log in.
Windows Defender Offline 
Windows Defender Offline (formerly known as Standalone System Sweeper Beta) is a bootable standalone antimalware program that runs from a bootable disk and is designed to scan infected systems while their operating systems are offline.
See also 
- Thurrott, Paul (24 October 2006). "Finally, Microsoft Ships Windows Defender". Windows IT Pro. Retrieved 8 May 2011.
- "Download: Windows® Defender". Microsoft Download Center. Microsoft Corporation. 23 May 2007. Retrieved 22 April 2011.
- "Download: Windows® Defender x64". Microsoft Download Center. Microsoft Corporation. 23 May 2007. Retrieved 22 April 2011.
- "Microsoft Product Lifecycle Search". Microsoft Support. Microsoft. Retrieved 3 November 2012.
- Thurrot, Paul (6 October 2010). "Microsoft Windows Anti-Spyware Preview: Paul Thurott's SuperSite for Windows". SuperSite for Windows. Retrieved 13 October 2011.
- "Microsoft Acquires Anti-Spyware Leader GIANT Company". PressPass. Microsoft. December 16, 2004. Retrieved 11 November 2009.
- "Gates Highlights Progress on Security, Outlines Next Steps for Continued Innovation". PressPass. Microsoft Corporation. February 15, 2005. Retrieved 11 November 2009.
- Thurrott, Paul (14 February 2006). "Windows Defender Beta 2 Review: Paul Thurrott's SuperSite for Windows". SuperSite for Windows. Retrieved 8 October 2009.
- "Windows Defender: Startseite" (in German). Microsoft Corporation. Archived from the original on 30 January 2009. Retrieved 8 May 2011.
- "マイクロソフト セキュリティ At Home" (in Japanese). Microsoft Corporation. Archived from the original on 18 January 2010. Retrieved 8 May 2011.
- Thurrott, Paul (18 June 2009). "Microsoft Security Essentials Public Beta". Paul Thurrott's SuperSite for Windows. Retrieved 8 May 2011.
- Hau, Kevin (23 June 2009). "Windows Defender and Microsoft Security Essentials". Microsoft Answers. Microsoft Corporation. Retrieved 8 May 2011.
- Marius, Marius Oiaga (30 August 2010). "Microsoft Security Essentials 1.0 and 2.0 Disable Windows Defender". Softpedia (SoftNews NET SRL). Retrieved 8 May 2011.
- Windows 8 Consumer Preview: Set Up Windows 8 with the Web Installer
- Microsoft Standalone System Sweeper
- "Windows Defender Offline". Microsoft.com. Microsoft. Retrieved 1 January 2012.