I have installed Zeroshell at a boarding shool. And I would like it to run alone with proxy, but without NAT, so students can do no filesharing etc. But if I do the settings that way, all sites with https are not accessible. But I would like the students to do webmailing from the websites of their providers. How is this possible?
Alternately, you can set up QoS rules for P2P networks and set the Maximum bandwidth to 1Kbps. Most P2P clients will drop the connection if the data rate is too slow. http://www.zeroshell.net/eng/qos/
However, this method is less absolute than the Firewall rules and some P2P connections may work despite the QoS rules.