Preface

Open source software is such an integral part of the Internet that is it safe to say that the Internet wouldn't exist as we know it today without it. The Internet never would have grown as fast and as dynamically as it did without open source programs such as BIND, which controls the domain name system; Sendmail, which powers most e-mail servers; INN, which runs many news servers; Major Domo, which runs many of the thousands of mailing lists on the Internet; and of course the popular Apache Web server. One thing for sure is that the Internet is a lot cheaper due to open source software. For that, you can thank the Free Software Foundation, BSD UNIX, Linux and Linus Torvalds, and the thousands of nameless programmers who put their hard work and sweat into the programs that run today's Internet.

While open source programs cover just about every aspect of computer software—from complete operating systems and games to word processors and databases—this book primarily deals with tools used in computer security. In the security field, there are programs that address every possible angle of IT security. There are open source firewalls, intrusion detection systems, vulnerability scanners, forensic tools, and cutting-edge programs for areas such as wireless communications. There are usually multiple choices in each category of mature, stable programs that compare favorably with commercial products. I have tried to choose the best of breed in each major area of information security (in my opinion, of course!). I present them in a detailed manner, showing you not just how to install and run them but also how to use them in your everyday work to have a more secure network. Using the open source software described in this book, you can secure your enterprise from both internal and external security threats with a minimal cost and maximum benefit for both the company and you personally.

I believe combining the concepts of information security with open source software offers one of the most powerful tools for securing your company's infrastructure, and by extension the entire Internet. It is common knowledge that large-scale virus infections and worms are able to spread because many systems are improperly secured. I believe that by educating the rank-and-file system managers and giving them the tools to get the job done, we can make the Internet more secure, one network at a time.