Microsoft Internet Security and Acceleration Server 2000

Developing Web (ISAPI) Filters for ISA

Web (ISAPI) filters detect and process HTTP events. Internet Security and Acceleration (ISA) Server 2000 supports ISAPI filter development and implementation, previously available only with Internet Information Services (IIS). ISA Server operates independently of IIS, while using the definition of ISAPI functions and structures provided in the Windows 2000 Software Development Kit (SDK). This topic provides information about ISAPI filters, as implemented in ISA.

In ISA Management and in the product documentation, ISAPI filters are referred to as Web filters.

For other general information regarding ISAPI filter development, see MSDN.

Note to Developers of Web filters for Internet Information Services

There are several differences between implementation of ISAPI in IIS and in ISA. These are described in ISAPI: Comparing IIS and ISA.

This section contains the following topics: