The network layer—layer three in the OSI Reference Model—is the primary mechanism for end-to-end routing and delivery of packet data on the Internet. This book is concerned mostly with attacks that are delivered over the IPv4 networking protocol, though many other networking protocols also exist, such as IPX, X.25, and the latent IPv6 protocol.

In this chapter, we'll focus first on how iptables logs network layer packet headers within log message output. Then we will see how these logs can be used to catch suspicious network layer activity.

Logging Network Layer Headers with iptables

With the iptables LOG target, firewalls built with iptables have the ability to write log data to syslog for nearly every ...

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