[Wlug] Snort.

Friends, Can you tell me to sniff detail informatstion using snort in linux in order to get sent and received information through my gateway. I have a firewall with snort installed, can I get details informations sent/received by my users where they are usig MSN Messanger, Yahoo Messanger, webmail, Outlook, etc ? Things I've done, just make a background precess and write it into file with snort, but the result is not so complettely as I need. How Can I sniff it so I can get detail information sent/received ? Thanks. Aramico