nstreams

"nstreams is a program that analyzes the networks streams occuring on a network and prints them in a human readable form. This is useful when you want to set up a firewall but do not know your needs/the needs of your customers. nstreams can read tcpdump output files or directly listen on a given interface, and may even produce ipchains (Linux) or ipfw (BSD) firewall rules instead of printing the streams, letting you build your firewall automagically." (Description on Freshmeat)