Snort 2.1 Intrusion Detection, Second Edition (Jay Beale's Open Source Security)

Called "the leader in the Snort IDS book arms race" by Richard Bejtlich, top Amazon reviewer, this brand-new edition of the best-selling Snort book covers all the latest features of a major upgrade to the product and includes a bonus DVD with Snort 2.1 and other utilities. Written by the same lead engineers of the Snort Development team, this will be the first book available on the major upgrade from Snort 2 to Snort 2.1 (in this community, major upgrades are noted by .x and not by full number upgrades as in 2.0 to 3.0). You will be given invaluable insight into the code base of Snort, and in depth tutorials of complex installation, configuration, and troubleshooting scenarios. Snort has three primary uses: as a straight packet sniffer, a packet logger, or as a full-blown network intrusion detection system. It can perform protocol analysis, content searching/matching and can be used to detect a variety of attacks and probes. Snort uses a flexible rules language to describe traffic that it should collect or pass, a detection engine that utilizes a modular plug-in architecture, and a real-time alerting capability. * The CD is not included with the ebook.

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The table of contents for "Snort 2.1" is deceiving, as it is almost exactly the same as "Snort 2.0." However, the new book is almost 200 pages larger than its predecessor, with many internal modifications. Chapters 1, 2, 3, 4, 9, 11, 12 and 13 are either completely new or substantially new. Chapters 5, 6, 7, 8, and 10 are either partial rewrites or have some material added or dropped. Despite all of this work, "Snort 2.1" fails to spend time on key subjects, which I will mention during a chapter-by-chapter examination of the book.

First, I recommend skipping ch 1. Aside from some general IDS advice, it is haphazard and contributes nothing to the core Snort discussion. Ch 2 is a quick overview of Snort capabilities, and should have been the lead chapter. Ch 3 describes Snort installation, but suffers apparently swapped figures (3.1 and 3.2) and a wrong figure (3.5). Ch 3 is still a nice upgrade from its counterpart in "Snort 2.0," which gave hints for deploying Snort on Red Hat Linux 8.0. The new ch 3 covers Linux, OpenBSD, and Windows.

Ch 4, "Inner Workings," is one of the reasons "Snort 2.1" has an advantage over the competition. It's tough to go wrong when Snort's developers describe the tool's operation. Still, signs of rough editing appear on p. 170 and 191, and the "-a cmg" switch should be "-A cmg".

Ch 5 covers rules, and is a big disappointment. For most users, rules are the primary means to customize Snort. Like "Snort 2.0," ch 5 fails to help readers with some of the more important new Snort rule options, like byte_test, byte_jump, distance, and within (available since 2.0.rc1 in Mar 03). Ch 5 implies on p. 145 that running Snort with -v is a good idea, despite every other recommendation in the book that verbose mode is a performance killer. Also, the IP "sec" option mentioned on p. 205 is not "IPSec" -- see RFC 791. Overall, ch 5 spends too much time restating rule information found in Snort's manual, and not enough time on features available even in Snort 2.0.

Ch 6's discussion of preprocessors is a solid chapter, with new material on Snort's flow module, http_inspect, and perfmonitor. The telnet preprocessor section is one of the better examples of a "code walkthrough," where the author shows code while explaining what it does.

Ch 7 is really showing its age. "Snort 2.0" was behind the times when it said "Unified logs are the future of Snort reporting," and "Snort 2.1" makes the same mistake. Barnyard, a means to read unified logs, was available in Sep 01! Ch 7 also misses the boat on XML output, calling it "our favorite and relatively new logging format" on p. 322. The XML plug-in spo_xml wasn't even part of snort-2.0.0, never mind snort-2.1.0. Basic research would have revealed Joe McAlerney's announcement of Silicon Defense's snort-idmef XML plug-in in Jun 01, followed by Sandro Poppi's assumption of the project in Aug 03. A mention of Barnyard's "XML formatting capabilities" appears in ch 7 on p. 322, yet Barnyard does not offer this natively.

I was happy to see Sguil addressed in ch 8, but sad to see Sguil's use of session and full content data not appreciated for its true worth. Ch 9 does a good job describing Oinkmaster and gives sound advice on avoiding the "not any" rule negation problem. Ch 10 covers really old testing tools like Sneeze, whose stateless operation cannot fool stream4's stateful inspection.

Ch 11, explaining Barnyard, is clearly the book's shining moment. This is the reason I read "Snort 2.1": Barnyard's author, Andrew Baker, describes Barnyard's history, the format of unified logs, and how best to use his contribution to Snort. Bravo. Ch 12 was also very good, using case studies to compare three different "active response" choices. Ch 13 was new but not exceptionally helpful.

I would enjoy seeing three improvements in the third edition. First, thoroughly scrub the book for old information. Watch out for people writing about "Cerebus" or http_decode or offerings from Silicon Defense, whose Web site disappeared in early 2004. Second, tell people to read the excellent Snort manual before reading the book. There's no need to address topics well-covered in the manual, like all of the IP- and TCP-based rule options. Third, ditch the existing rules chapter in favor of two new ones, one explaining principles via existing rules, and one showing advanced rule development.

I still recommend buying this book, but you might guide your reading choices by the comments in this review.

5 of 5 found the following review helpful:

Detailed information for IDS systems and Snort in particularJul 15, 2004
By Harold McFarland
If you want to know about Snort 2.1, one of the best open source intrusion detections systems available, then "Snort 2.1 Intrusion Detection, Second Edition" is the book you will want to have. This is an extensive examination of the Snort program and includes Snort 2.1 on CD with the Book.

The authors start with defining what an intrusion detection system is, what it is not, and how placing it in your network at different points achieves different goals. This is followed by an introduction to Snort and a description of its capabilities and functions before getting into the nuts and bolts of installing and configuring it.

One of the more difficult parts of Snort to understand is how to write the rules that determine when an intrusion has occurred. The authors do an excellent job of describing exactly how to write good rules to achieve the results you want. They even include an excellent section on how to deal with all that information you will be collecting.

"Snort 2.1 Intrusion Detection, Second Edition" is highly recommended for anyone who wants a good, useful explanation of how an intrusion detection system should work and how to implement Snort to achieve that result.

1 of 1 found the following review helpful:

mighty impressive second editionJun 30, 2004
By Seth James
I was concerned this book may fall into the "second edition trap" of search and replace 2.0 with 2.1. Upon thorough reading, this is obviously not the case. The authors have thoroughly documented all new/enhanced features of 2.1, but more importantly they again break new ground by by providing unique, creative, and thoroughly useful information on things like writing rules, the intricacises of preprocessors, etc. They don't just teach you how to USE snort, they teach you how to think about using Snort (and other tools) to better defend your network. The chapter on Barnyard in particular was very interesting, and it's obvious from following following the Snort site/list that a lot of the new features were develped in conjunction with the writing of this book. So, this book isn't a re-hash of information, it's the definitive work from the creators.

Snort 2.1Feb 23, 2006
By Jon T. Mccombs
The information in this book was invalueable but sometimes it was hard to follow because it was poorly written

Good introductionto SnortNov 28, 2005
By Daniel Owen
Snort 2.1 Intrusion Detection (2nd Edition) is useful as a general introduction to intrusion detection and Snort. If you already have a good understanding of IDS technology you may find the IDS discussion to be a bit general in nature. For someone who only wants to review the basic IDS principals quickly and without a great deal of extra detail the IDS coverage in this book is sufficient. Much of the information on Snort felt like a retelling of Snort Users Manual from the Snort web site. Part of this feeling may be due to the fact that members of the Snort development team who undoubtedly had a hand in the user's manual wrote this book. This book does go into more detail on some subjects than the Snort Users Manual. There is a good step by step set of instructions for installing Snort and associated software on either a Windows or a Linux system. Overall this book seems to be a pretty good overview of Snort for someone looking to use only one resource, but I do not see anything that is not also available in other documentation available.

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