Topic: Application-level filtering

I don't really have a specific use at the moment, but I find it interesting nonetheless. Do any of you know about programs available that will let me filter the actual contents of packets, not just the source/destination/protocol information?

I know there are web proxies that can go a little deeper (mainly URL-based filters), but I'm looking for something more generic than that. For example, a filter that would let me block one channel on an IRC server by picking out its related packets.

Re: Application-level filtering

What you're asking for is a generic proxy server that understands application-specific protocols. I hope you see the contradiction there.

I guess you could implement a proxy that just searches for given stings inside the connection stream, and kills a connection if the string, say,

Re: Application-level filtering

I wasn't expecting for the protocols to be understood (though it would be nice if patterns/templates could be used). I just wanted to know if there was any firewall that could at least allow some level of filtering based on packet contents.