Microsoft Internet Security and Acceleration Server 2000

Introduction to Web Filters

Web (ISAPI) filters allow you to intervene in the processing of HTTP requests. Web filters are dynamic-link libraries (DLLs) that are loaded when the ISA Web proxy (w3proxy) service is started and stay in memory until the service shuts down. Web filters can be configured to receive filter-event notifications that occur with each HTTP request that the ISA Web proxy service receives and with each response returned through the Web proxy by an external Web server.

The following illustration provides a schematic overview of the HTTP request-and-response process. A Web filter can register for and react to the events represented in the illustration.

This section contains the following topics: