For the most part, my writing career has centered on describing how to implement and use software that I didn't write. I am therefore much indebted to and even a little in awe of the hundreds of outstanding programmers who create the operating systems and applications I use and write about. They are the rhinoceroses whose backs I peck for insects.

As if I weren't beholden to those programmers already, I routinely seek and receive first-hand advice and information directly from them. Among these generous souls are Jay Beale of the Bastille Linux project, Ron Forrester of Tripwire Open Source, Balazs "Bazsi" Scheidler of Syslog-ng and Zorp renown, and Renaud Deraison of the Nessus project.

Special thanks go to Dr. Wietse Venema of the IBM T.J. Watson Research Center for reviewing and helping me correct the SMTP chapter. Not to belabor the point, but I find it remarkable that people who already volunteer so much time and energy to create outstanding free software also tend to be both patient and generous in returning email from complete strangers.

Bill Lubanovic wrote the section on djbdns in Chapter 4, and all of Chapter 6, ? brilliantly, in my humble opinion. Bill has added a great deal of real-world experience, skill, and humor to those two chapters. I could not have finished this book on schedule (and its web security chapter, in particular, would be less convincing!) without Bill's contributions.

I absolutely could not have survived juggling my day job, fatherly duties, magazine column, and resulting sleep deprivation without an exceptionally patient and energetic wife. This book therefore owes its very existence to Felice Amato Bauer. I'm grateful to her for, among many other things, encouraging me to pursue my book proposal and then for pulling a good deal of my parental weight in addition to her own after the proposal was accepted and I was obliged to actually write the thing.

Linux Journal and its publisher, Specialized Systems Consultants Inc., very graciously allowed me to adapt a number of my "Paranoid Penguin" columns for inclusion in this book: Chapter 1 through Chapter 5, plus Chapter 8, Chapter 10, and Chapter 11 contain (or are descended from) such material. It has been and continues to be a pleasure to write for Linux Journal, and it's safe to say that I wouldn't have had enough credibility as a writer to get this book published had it not been for them.

My approach to security has been strongly influenced by two giants of the field whom I also want to thank: Bruce Schneier, to whom we all owe a great debt for his ongoing contributions not only to security technology but, even more importantly, to security thinking; and Dr. Martin R. Carmichael, whose irresistible passion for and unique outlook on what constitutes good security has had an immeasurable impact on my work.

It should but won't go without saying that I'm very grateful to Andy Oram and O'Reilly & Associates for this opportunity and for their marvelous support, guidance, and patience. The impressions many people have of O'Reilly as being stupendously savvy, well-organized, technologically superior, and in all ways hip are completely accurate.

A number of technical reviewers also assisted in fact checking and otherwise keeping me honest. Rik Farrow, Bradford Willke, and Joshua Ball, in particular, helped immensely to improve the book's accuracy and usefulness.

Finally, in the inevitable amorphous list, I want to thank the following valued friends and colleagues, all of whom have aided, abetted, and encouraged me as both a writer and as a "netspook": Dr. Dennis R. Guster at St. Cloud State University; KoniKaye and Jerry Jeschke at Upstream Solutions; Steve Rose at Vector Internet Services (who hired me way before I knew anything useful); David W. Stacy of St. Jude Medical; the entire SAE Design Team (you know who you are ? or do you?); Marty J. Wolf at Bemidji State University; John B. Weaver (whom nobody initially believes can possibly be that cool, but they soon realize he can `cause he is); the Reverend Gonzo at; Richard Vernon and Don Marti at Linux Journal; Jay Gustafson of Ingenious Networks; Tim N. Shea (who, in my day job, had the thankless task of standing in for me while I finished this book), and, of course, my dizzyingly adept pals Brian Gilbertson, Paul Cole, Tony Stieber, and Jeffrey Dunitz.