?Finders?

Someone told me today that a FINDER is a snippet of code that checks remote IPs and blocks against unwanted hosts. One way I thought of doing this is from the calling server the link is a form submit (post method) which contains the HTTP_SERVER_VARS["LOCAL_ADDR"] of the server in the post info. My script checks it against a list of allowables and passes or dies. Is there another way besides submitting a form? I tried using HTTP_SERVER_VARS["REMOTE_ADDR"] but that returns the client the IP not the referring IP. Are they called FINDERS? I couldn't find anything while searching around the net for info on the idea. Any comments are welcome Thanks RDB