Microsoft Internet Information Services (IIS; formerly called Server) is a set of Internet-based services for servers using Microsoft Windows. It is the world's second most popular web server in terms of overall websites. As of August 2007 it served 34.28% of all websites and 36.21% of all active websites according to Netcraft. The servers currently include FTP, SMTP, NNTP and HTTP/HTTPS.

Versions
IIS was initially released as an additional set of Internet based services for Windows NT 3.51. IIS 2.0 followed adding support for the Windows NT 4.0 operating system and IIS 3.0 introduced the Active Server Pages dynamic scripting environment.
IIS 4.0 dropped support for the Gopher protocol and was bundled with Windows NT as a separate "Option Pack" CD-ROM.
The current shipping version of IIS is 7.0 for Windows Vista, 6.0 for Windows Server 2003 and IIS 5.1 for Windows XP Professional. IIS 5.1 for Windows XP is a restricted version of IIS that supports only 10 simultaneous connections and a single web site. IIS 6.0 added support for IPv6.
Windows Vista does not install IIS 7.0 by default, but it can be selected among the list of optionally installed components. IIS 7.0 on Vista does not limit the number of connections allowed rather restricts performance based on active concurrent requests.

History of IIS
Earlier versions of IIS were hit with a spate of vulnerabilities, chief among them CA-2001-19 which led to the infamous Code Red worm; however, version 7.0 currently has no reported issues that affect it. In perspective, the free software Apache web server has four reported issues,, a default Windows account with elevated rights. Under 6.0 all request handling processes have been brought under a Network Services account which has significantly fewer privileges. In particular this means that if there is an exploit in a feature or custom code, it wouldn't necessarily compromise the entire system given the sandboxed environment the worker processes run in. IIS 6.0 also contained a new kernel HTTP stack (http.sys) with a stricter HTTP request parser and response cache for both static and dynamic content.

Internet Information Services 7.0

List of FTP servers
List of mail servers
Comparison of web servers
WISA
Metabase
ASP.NET