When ten plus people are yelling at you at the same time, who do you listen to? It wouldn't matter if everyone was yelling out the scores from yesterday's ball game, however, what if they were yelling about which box / server / service is down? Organize and get your battle plan set by having Nagios sort it all out for you. In fact, make sure everything is working properly with a secured SSH server first and you'll have an easier time bouncing around your network to mitigate any damages.

There isn't an easy and automated way to monitor open ports in Red Hat Enterprise Linux 5 (RHEL 5), says the author of Hardening Linux, James Turnbull. However, you can scan with some handy open source tools. Turnbull recommends using hardscan, a Netstat-based tool, if you think you have been compromised.

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