There is actualy a couple of ways to block gnutella. One is to clober it at the head end router, the other is with a firewall package like Firewall1 which can do content filtering. There is a 3rd way which won't block gnutella but will effectively make it not work. And that is to do rate shapping of the ip packets. Basicly rate shapping allows you to specify the amount of band-width for certain ports and/or applications. If you therotled back gnutella to say 8k, the client would spend all day just trying to make a connection, and when it did, it would be like surfing a real real real slow web site. Being a network manager at Central Michigan University, i've had to clobber gnutella because the students were using almost 100mb of my OC3 (155mb) connection just on sharing out mp3's! I didn't like it, but that was the only way we could keep up Internet connectivity for the rest of campus. I'm pretty sure your school had to do the same thing for the same reason.