Chapter 11. Network Intrusion Detection

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One type of tool that’s come to the forefront in network security in recent years is the network intrusion detection system (NIDS). These systems can be deployed on your network and monitor the traffic until they detect suspicious behavior, when they spring into action and notify you of what is going on. They are excellent tools to use in addition to your logs, since a network IDS can often spot an attack before it reaches the intended target or has a chance to end up in your logs.

Currently, there are two main types of NIDS. The first type detects intrusions by monitoring network traffic for specific byte patterns that are similar to known attacks. A NIDS that operates in this manner is known as a signature-based intrusion detection system. The other type of network IDS is a statistical monitor. These systems also monitor the traffic on the network, but instead of looking for a particular pattern or signature, they maintain a statistical history of the packets that pass through the network and report when they see a packet that falls outside of the normal network traffic pattern. NIDSs that employ this method are known as anomaly-based intrusion detection systems.

In this chapter, you’ll learn how to set up Snort, a signature-based IDS. You’ll also learn how to set up Snort with SPADE, which adds anomaly-detection capabilities to Snort, giving you the best of both worlds. This chapter also demonstrates how to set up several ...

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