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Overview of ISA Server

Updated: March 28, 2003

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

ISA Server offers a complete Internet connectivity deployment solution as a firewall and a Web caching server.


  • ISA Server (the successor to Proxy Server 2.0) is a separate product from the Microsoft® Windows® Server 2003 operating system. You must install ISA Server Service Pack (SP1) for ISA Server immediately after installing ISA Server for it to be interoperable with Windows Server 2003.

ISA Server monitors requests and responses between the Internet and internal client computers; ISA Server also controls which computers on the Internet the internal clients can access.

ISA Server offers many security and caching options, including:

  • Enhanced security with multilayer firewall and integrated intrusion detection.

    ISA is a complete firewall product that provides packet filtering, stateful packet inspection and application-level awareness for many common protocols, such as Simple Mail Transfer Protocol (SMTP) and Domain Name System (DNS). You can create access policies based on user-level information, IP addresses, or Web content.

  • Secure publishing.

    You can use ISA Server as a reverse cache server to define a secure publishing policy. This protects internal publishing servers and makes them safely accessible to Internet clients.

  • ISA Server can cache Web content, potentially reducing your external bandwidth requirements.

    You can configure the cache to contain content that your organization uses frequently or that your Internet clients access.

  • ISA Server is extensible.

    You can program the COM interface in ISA Server using high-level programming languages or scripting languages. Developers can implement application and web filters to extend the core firewall functionality. You can use the ISA Server management interface to develop additional administration tools and management scripts.

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