Chapter 2. Implement Policies for Monitoring

My first college apartment had a terrible cockroach problem. Upon returning from a date one evening, I was shocked to see dozens of them scatter away from an empty pizza box when I turned on the lights. After that, it was tough to push away the idea that cockroaches were everywhere—I expected to see them in every corner of the apartment. The first time I fired up Snort I was reminded of that experience; suddenly I could see what was crawling through the network, and I wanted to fix it all at once.

It’s easy to get sucked into bug stomping: once you see what’s on the network, you have the urge to fix and explain every security event you discover. Here’s where the analogy ends, though, for not everything on the wire is a cockroach. Much of the traffic is perfectly fine, if ugly. Once you understand that its ugliness is not a security threat, you can safely let it through. By narrowing your focus to the truly threatening traffic, you can turn your full attention to stomping it out.

Historically, security monitoring tools have demonstrated their worth by showing the cockroaches: they illuminate the dark corners to show you how well they’re performing their task. Once you’re convinced of a cockroach problem, you need a plan for dealing with the problem, and that plan will likely involve prevention and detection.

A security guard could easily be fooled if his practice was to investigate every movement detected by security cameras. He must work ...

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