An Internet-connected Linux machine is in a high-risk situation. Linux Firewalls, Third Edition details security steps that any sized implementation--from home use to enterprise level--might take to protect itself from potential remote attackers. As with the first two editions, this book is especially useful for its explanations of iptables, packet filtering, and firewall optimization along with some advanced concepts including customizing the Linux kernel to enhance security.The third edition, while distribution neutral, has been updated for the current Linux Kernel and provides code examples for Red Hat, SUSE, and Debian implementations. Don't miss out on the third edition of the critically acclaimed Linux Firewalls.

Just how interesting packets turn out to be is revealed in Linux Firewalls, Robert L. Zeigler's sober, agile, and subtle text. Narrowing consideration to threats faced by small networks from external sources, Zeigler and his editors introduce security by delivering prerequisite tutorials on packet architecture and normal network-based client/server daemon-to-daemon communications. Nonthreatening daemon-to-daemon communication is part of the regular operation of a networked POSIX-compliant operating system (like Linux or Windows NT), but the incessant background chatter makes finding hostile intrusions a search for sometimes subtle irregularities in a high throughput environment.

In fact, bombardment of networks with useless packets can create diversions for more pernicious attacks. Distinguishing the good packets from the potentially hostile or merely useless packets requires levels of filtering criteria that depend on the specifics of the network environment. Zeigler sorts out all of these issues and outlines practical network administration strategies for packet filtering.

Linux Firewalls is a how-to for the home Linux box, including the creating and debugging firewall rules for home LANs and network interfaces. For larger LAN users, Zeigler describes intrusion logging; configurations based on varying levels of trust; and the how, why, and when of reporting intrusions to network authorities.

In the wrong hands, firewall reports are either hyped-up cloak-and-dagger sensationalism or monotonous treatises in bitwise accounting. Zeigler strikes a middle ground with a book fit for members of the Linux community who are curious about what is happening over their TCP/IP connections. These are folks who have the prowess to build kernel releases on their own but who aren't necessarily wonks at developing kernel or device driver sources. --Peter Leopold