From Linux Support itmission.org

Main: How-do-i-block-p2p-traffic

• ipp2p is a reasonable stable product.

Please do find out more about the product at the link below.

ipp2p

• L7-filter is a classifier for Linux's Netfilter that identifies packets based on application layer data.

It can classify packets as Kazaa, HTTP, Jabber, Citrix, Bittorrent,FTP, Gnucleus, eDonkey2000, etc.

http://sf.net/projects/l7-filter/

• Also if user tunnel packets through SSL or uses encrypt them, none of these technique will work as software classify them as SSL
• The goal of the IPP2P project is to identify peer-to-peer (P2P)

                  http://www.ipp2p.org