The Microsoft Internet API for IIS, ISAPI, sits between the client and the Web server. Therefore, you can access the HTTP data stream before IIS gets to see it. The project in this article takes advantage of the ISAPI architecture to create a filter that monitors access to a Web site to determine if visits are from typical users or from automated processes designed to pilfer information from your site. The author tracks the regularity of visits to the site to determine the likely source. Once the determination is made, the app either redirects the user or continues to track information about those hits.
MSDN Magazine October 2001
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