Java has grown by leaps and bounds since its introduction in 1996, and is now among the most popular computing platforms on the planet. Java has evolved and changed so much that at a mere two-years old, our original work, Java Security: Hostile Applets, Holes, and Antidotes, found itself in serious need of revision and expansion. This book is the result of several years of thinking about mobile code and security, and includes many things we have discovered while working on real-world systems with businesses and government agencies. Our goal is to present enough information to help you separate fact from fiction when it comes to mobile code security.

Java has become much more complicated and multifaceted than it was when it was introduced. No longer simply a client-side language for applets, Java can now be found on everything from enterprise application servers to embedded devices like smart cards. We have tried to address security factors from throughout the entire Java range in this book.

We hope this book appeals to geeks and grandmothers alike (not that some grandmothers aren't geeks). Although it gets technical in places, we hope the messages are clear enough that even the casual Web user comes away with a broader understanding of the security issues surrounding mobile code. We kept four groups in mind as we wrote this book: Web users, developers, system administrators, and business decision-makers. Many of the issues of mobile code security cut across these groups. As Java integrates itself into the foundations of electronic commerce, Java security issues take on more urgency.

Java is only one kind of mobile code among many. Other systems immersed in the same security dilemma include ActiveX, JavaScript, and Word Macros. It is essential not to get the wrong message from this book. Our focus on Java is no accident. We believe Java is the most viable mobile code system created to date. Don't believe that through our work we imply that other systems are any more secure than Java. Just the opposite is true.

With the introduction of code signing to Java (in JDK 1.1) and its enhancement with access control (in Java 2), securing Java became much harder. Java's position along the security/functionality tradeoff has moved significantly toward functionality, to the detriment of security. This is good if you want more functionality, which most businesses and developers seem to need, but it is bad if you are charged with managing security risks. Forming an intelligent Java use policy is more important than ever, but doing so is more complicated than it used to be.

The computer field moves so fast that people have begun to refer to Internet time to grapple with its constantly accelerating speed. Three months is a year in Internet time. Java is directly involved in the speed of the field, and has done its share to make things move even more quickly. One tricky aspect of writing a topical book relating to the Web is figuring out when to stop the action. This process can be likened to freeze-framing a picture of a movie. In that sense, this book is a snapshot of Java security. We hope we have succeeded in making it a useful way to learn about Java security. For up-to-date information, see the book's companion Web site at www.rstcorp.com/java-security.html.

As we went to press, Sun Microsystems renamed JDK 1.2 and called it Java 2. We have attempted to use correct version numbers throughout and apologize for any confusion.

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