Ngrep and p2p
This the command I use to track down P2P conenctions
p2p
Linux Kernel 2.6.24 with iptables 1.4.0, ipp2p -0.8.2 and L7-filter 2.17
Linux Kernel 2.6.24 with iptables 1.4.0,
Traffic Shaping on Linux Gateway with tc , iptables and ipp2p
Original Article here
[http://suchart.wordpress.com/2007/12/17/