Logging\Filtering Packets Through a Gateway
Ok, here's my issue. People behind my firewall (who are technically incompetant) are giving out information about the internal network, and also executing commands that outside people tell them. They are talking to these people over MSN, AIM, those kinds of things. Sadly, these people are trying to find leaks in my firewall, so I am trying to stop them. I was wondering if it was possible to actively check all the appropriate packets for certain phrases or bits of information and drop the ones that contain it, and also log them?
What tools should I use? Any tutorials that would help?