Search Appliance
The Thunderstone ISAPI Proxy Module is an IIS add-on that allows you to proxy requests through another machine.
Users' search requests are not made directly to the Search Appliance, but to the Proxy Module, which then passes the request along to the Search Appliance.
The Proxy Module also has an optional AuthProxy, which allows the use of automatic Active Directory credentials when authenticating the Search Appliance search results. Internet Explorer will be configured to automatically pass along the authentication information, allowing for Single Sign On. The Search Appliance communicates with the Proxy Module to authorize the results.