Preface

"Trust no one."

Aside from being the motto and modus operandi for the successful TV series The X Files, it is also a beneficial mantra to practice in all facets of security and investigation. Even though chances are good that you won't encounter Mulder, Scully, and their gang, they still teach a concept that's become increasingly relevant as the world—and the world's computers—become connected.

Companies today are increasingly basing their business models around providing access to resources—web pages, Internet access, email accounts, or anything else—that need to be protected. How does a user indicate to a system, especially one that indeed trusts no one, that he's entitled to use that computer's services? How can the owner of a business keep non-paying users out of the way while providing convenient access to paying customers? The bottom line is this: with new security exploits being uncovered every day and the general environment of the Internet public degenerating from a trusted environment into one of hostility and attack, there has to be some way in which an Internet citizen can use resources to which he's entitled without letting everybody else in the gates.

This is the purpose of the RADIUS protocol—to differentiate, secure, and account for these users. And the purpose of this book is to provide the most complete reference to RADIUS possible.