Snort, fyi, is an Intrusion Detection System, which means a bit of software designed to catch hackers as they try to penetrate your computer or network.

While this software is usually run on regular Unix servers, Nick Zitzmann has kindly created an all-in-one package that lets you run Snort natively on MacOS X with a much friendlier graphical interface for configuring the thing. This gem is called HenWen and can be found here: http://www.versiontracker.com/dyn/moreinfo/macosx/14778 Note that this product contains all you need to run Snort but does not contain the tools to analyze the output from Snort: that's where SAM can come in and help.

And, yes, any security professional will tell you that you cannot run a LAN nowadays without an IDS and hope to escape the hackers unscathed...