icappfd is an ICAP daemon that can scan and change responses received from an HTTP server.
It scans content for phrases, assigns a score to a page and will redirect to a block url for each page with a score that passes a pre-configured limit...
It's kinda like a spam filter for the web.
icappfd is used with proxy servers (squid3, and probably others) to protect users from certain types of content such as gambling, peer2peer, porn etc etc.