Preface to Security in Computing, 5th Edition
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Tablets, smartphones, TV set-top boxes, GPS navigation devices, exercise monitors, home security stations, even washers and dryers come with Internet connections by which data from and about you go to places over which you have little visibility or control. At the same time, the list of retailers suffering massive losses of customer data continues to grow: Home Depot, Target, T.J. Maxx, P.F. Chang’s, Sally Beauty. On the one hand people want the convenience and benefits that added connectivity brings, while on the other hand, people are worried, and some are seriously harmed by the impact of such incidents. Computer security brings these two threads together as technology races forward with smart products whose designers omit the basic controls that can prevent or limit catastrophes.
To some extent, people sigh and expect security failures in basic products and complex systems. But these failures do not have to be. Every computer professional can learn how such problems occur and how to counter them. Computer security has been around as a field since the 1960s, and it has developed excellent research, leading to a good understanding of the threat and how to manage it.
One factor that turns off many people is the language: Complicated terms such as polymorphic virus, advanced persistent threat, distributed denial-of-service attack, inference and aggregation, multifactor authentication, key exchange protocol, and intrusion detection system do not exactly roll off the tongue. Other terms sound intriguing but opaque, such as worm, botnet, rootkit, man in the browser, honeynet, sandbox, and script kiddie. The language of advanced mathematics or microbiology is no less confounding, and the Latin terminology of medicine and law separates those who know it from those who do not. But the terms and concepts of computer security really have straightforward, easy-to-learn meaning and uses.
Vulnerability: weakness
Threat: condition that exercises vulnerability
Incident: vulnerability + threat
Control: reduction of threat or vulnerablity
The premise of computer security is quite simple: Vulnerabilities are weaknesses in products, systems, protocols, algorithms, programs, interfaces, and designs. A threat is a condition that could exercise a vulnerability. An incident occurs when a threat does exploit a vulnerability, causing harm. Finally, people add controls or countermeasures to prevent, deflect, diminish, detect, diagnose, and respond to threats. All of computer security is built from that simple framework. This book is about bad things that can happen with computers and ways to protect our computing.
Why Read This Book?
Admit it. You know computing entails serious risks to the privacy of your personal data, the integrity of your data, or the operation of your computer. Risk is a fact of life: Crossing the street is risky, perhaps more so in some places than others, but you still cross the street. As a child you learned to stop and look both ways before crossing. As you became older you learned to gauge the speed of oncoming traffic and determine whether you had the time to cross. At some point you developed a sense of whether an oncoming car would slow down or yield. We hope you never had to practice this, but sometimes you have to decide whether darting into the street without looking is the best means of escaping danger. The point is all these matters depend on knowledge and experience. We want to help you develop comparable knowledge and experience with respect to the risks of secure computing.
The same thing can be said about computer security in everything from personal devices to complex commercial systems: You start with a few basic terms, principles, and concepts. Then you learn the discipline by seeing those basics reappear in numerous situations, including programs, operating systems, networks, and cloud computing. You pick up a few fundamental tools, such as authentication, access control, and encryption, and you understand how they apply in defense strategies. You start to think like an attacker, predicting the weaknesses that could be exploited, and then you shift to selecting defenses to counter those attacks. This last stage of playing both offense and defense makes computer security a creative and challenging activity.
Uses for and Users of This Book
This book is intended for people who want to learn about computer security; if you have read this far you may well be such a person. This book is intended for three groups of people: college and university students, computing professionals and managers, and users of all kinds of computer-based systems. All want to know the same thing: how to control the risk of computer security. But you may differ in how much information you need about particular topics: Some readers want a broad survey, while others want to focus on particular topics, such as networks or program development.
This book should provide the breadth and depth that most readers want. The book is organized by general area of computing, so that readers with particular interests can find information easily.
Organization of This Book
The chapters of this book progress in an orderly manner, from general security concerns to the particular needs of specialized applications, and then to overarching management and legal issues. Thus, this book progresses through six key areas of interest:
- Introduction: threats, vulnerabilities, and controls
- The security practitioner’s “toolbox”: identification and authentication, access control, and encryption
- Application areas of computer security practice: programs, user–Internet interaction, operating systems, networks, data and databases, and cloud computing
- Cross-cutting disciplines: privacy, management, law and ethics
- Details of cryptography
- Emerging application domains
The first chapter begins like many other expositions: by laying groundwork. In Chapter 1 we introduce terms and definitions, and give some examples to justify how these terms are used. In Chapter 2 we begin the real depth of the field by introducing three concepts that form the basis of many defenses in computer security: identification and authentication, access control, and encryption. We describe different ways of implementing each of these, explore strengths and weaknesses, and tell of some recent advances in these technologies.
Then we advance through computing domains, from the individual user outward. In Chapter 3 we begin with individual programs, ones you might write and those you only use. Both kinds are subject to potential attacks, and we examine the nature of some of those attacks and how they could have been prevented. In Chapter 4 we move on to a type of program with which most users today are quite familiar: the browser, as a gateway to the Internet. The majority of attacks today are remote, carried from a distant attacker across a network, usually the Internet. Thus, it makes sense to study Internet-borne malicious code. But this chapter’s focus is on the harm launched remotely, not on the network infrastructure by which it travels; we defer the network concepts to Chapter 6. In Chapter 5 we consider operating systems, a strong line of defense between a user and attackers. We also consider ways to undermine the strength of the operating system itself. Chapter 6 returns to networks, but this time we do look at architecture and technology, including denial-of-service attacks that can happen only in a network. Data, their collection and protection, form the topic of Chapter 7, in which we look at database management systems and big data applications. Finally, in Chapter 8 we explore cloud computing, a relatively recent addition to the computing landscape, but one that brings its own vulnerabilities and protections.
In Chapters 9 through 11 we address what we have termed the intersecting disciplines: First, in Chapter 9 we explore privacy, a familiar topic that relates to most of the six domains from programs to clouds. Then Chapter 10 takes us to the management side of computer security: how management plans for and addresses computer security problems. Finally, Chapter 11 explores how laws and ethics help us control computer behavior.
We introduced cryptography in Chapter 2. But the field of cryptography involves entire books, courses, conferences, journals, and postgraduate programs of study. And this book needs to cover many important topics in addition to cryptography. Thus, we made two critical decisions: First, we treat cryptography as a tool, not as a field of study. An automobile mechanic does not study the design of cars, weighing such factors as aerodynamics, fuel consumption, interior appointment, and crash resistance; a mechanic accepts a car as a given and learns how to find and fix faults with the engine and other mechanical parts. Similarly, we want our readers to be able to use cryptography to quickly address security problems; hence we briefly visit popular uses of cryptography in Chapter 2. Our second critical decision was to explore the breadth of cryptography slightly more in a later chapter, Chapter 12. But as we point out, entire books have been written on cryptography, so our later chapter gives an overview of more detailed work that interested readers can find elsewhere.
Our final chapter detours to four areas having significant computer security hazards. These are rapidly advancing topics for which the computer security issues are much in progress right now. The so-called Internet of Things, the concept of connecting many devices to the Internet, raises potential security threats waiting to be explored. Economics govern many security decisions, so security professionals need to understand how economics and security relate. Convenience is raising interest in using computers to implement elections; the easy steps of collecting vote totals have been done by many jurisdictions, but the hard part of organizing fair online registration and ballot-casting have been done in only a small number of demonstration elections. And the use of computers in warfare is a growing threat. Again, a small number of modest-sized attacks on computing devices have shown the feasibility of this type of campaign, but security professionals and ordinary citizens need to understand the potential—both good and bad—of this type of attack.
How to Read This Book
What background should you have to appreciate this book? The only assumption is an understanding of programming and computer systems. Someone who is an advanced undergraduate or graduate student in computing certainly has that background, as does a professional designer or developer of computer systems. A user who wants to understand more about how programs work can learn from this book, too; we provide the necessary background on concepts of operating systems or networks, for example, before we address the related security concerns.
This book can be used as a textbook in a one- or two-semester course in computer security. The book functions equally well as a reference for a computer professional or as a supplement to an intensive training course. And the index and extensive bibliography make it useful as a handbook to explain significant topics and point to key articles in the literature. The book has been used in classes throughout the world; instructors often design one-semester courses that focus on topics of particular interest to the students or that relate well to the rest of a curriculum.
What Is New in This Book
This is the fifth edition of Security in Computing, first published in 1989. Since then, the specific threats, vulnerabilities, and controls have changed, as have many of the underlying technologies to which computer security applies. However, many basic concepts have remained the same.
Most obvious to readers familiar with earlier editions will be some new chapters, specifically, on user–web interaction and cloud computing, as well as the topics we raise in the emerging topics chapter. Furthermore, pulling together the three fundamental controls in Chapter 2 is a new structure. Those are the big changes, but every chapter has had many smaller changes, as we describe new attacks or expand on points that have become more important.
One other feature some may notice is the addition of a third coauthor. Jonathan Margulies joins us as an essential member of the team that produced this revision. He is currently director of the security practice at Qmulos, a newly launched security consulting practice. He brings many years of experience with Sandia National Labs and the National Institute for Standards and Technology. His focus meshes nicely with our existing skills to extend the breadth of this book.
Acknowledgments
It is increasingly difficult to acknowledge all the people who have influenced this book. Colleagues and friends have contributed their knowledge and insight, often without knowing their impact. By arguing a point or sharing explanations of concepts, our associates have forced us to question or rethink what we know.
We thank our associates in at least two ways. First, we have tried to include references to their written works. References in the text cite specific papers relating to particular thoughts or concepts, but the bibliography also includes broader works that have played a more subtle role in shaping our approach to security. So, to all the cited authors, many of whom are friends and colleagues, we happily acknowledge your positive influence on this book.
Rather than name individuals, we thank the organizations in which we have interacted with creative, stimulating, and challenging people from whom we learned a lot. These places include Trusted Information Systems, the Contel Technology Center, the Centre for Software Reliability of the City University of London, Arca Systems, Exodus Communications, The RAND Corporation, Sandia National Lab, Cable & Wireless, the National Institute of Standards and Technology, the Institute for Information Infrastructure Protection, Qmulos, and the Editorial Board of IEEE Security & Privacy. If you worked with us at any of these locations, chances are high that your imprint can be found in this book. And for all the side conversations, debates, arguments, and light moments, we are grateful.
About the Authors
Charles P. Pfleeger is an internationally known expert on computer and communications security. He was originally a professor at the University of Tennessee, leaving there to join computer security research and consulting companies Trusted Information Systems and Arca Systems (later Exodus Communications and Cable and Wireless). With Trusted Information Systems he was Director of European Operations and Senior Consultant. With Cable and Wireless he was Director of Research and a member of the staff of the Chief Security Officer. He was chair of the IEEE Computer Society Technical Committee on Security and Privacy.
Shari Lawrence Pfleeger is widely known as a software engineering and computer security researcher, most recently as a Senior Computer Scientist with the Rand Corporation and as Research Director of the Institute for Information Infrastructure Protection. She is currently Editor-in-Chief of IEEE Security & Privacy magazine.
Jonathan Margulies is the CTO of Qmulos, a cybersecurity consulting firm. After receiving his master’s degree in Computer Science from Cornell University, Mr. Margulies spent nine years at Sandia National Labs, researching and developing solutions to protect national security and critical infrastructure systems from advanced persistent threats. He then went on to NIST’s National Cybersecurity Center of Excellence, where he worked with a variety of critical infrastructure companies to create industry-standard security architectures. In his free time, Mr. Margulies edits the “Building Security In” section of IEEE Security & Privacy magazine.