A set of Internet-based services for Windows machines, sometimes refers to as Internet Information Services or System. Originally IIS was supplied as part of the Option Pack for Windows NT to expand it's capabilities to include the ability to serve web pages. Subsequently, IIS was integrated with Windows 2000 and Windows Server 2003. The current version is IIS 6.0 and includes servers for FTP, SMTP, NNTP and HTTP/ HTTPS. For more information, visit Microsoft's Internet Information Services web page. Abbreviation: IIS.