Chapter 1. Perimeter Security Fundamentals

The security of your network is evaluated daily. A rich question to ask is, “Are you the one doing it?” The answer, hopefully, is that someone on your side is involved in assessing the effectiveness of your defenses; however, overwhelming evidence reports that you are not the only party probing your network's perimeter. Internet-facing systems—computers with IP addresses that can be reached from the Internet—receive between several and hundreds or even thousands of attack attempts every day. Many of these are simple scans that we know how to defend against, but others catch us by surprise, unexpectedly shifting us into incident investigation and cleanup mode.

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