Prentice Hall Security In Computing 4th Edition Oct 2006 ISBN 0132390779

  Security in Computing, Fourth Edition By Charles P. Pfleeger - Pfleeger Consulting Group,

Shari Lawrence Pfleeger - RAND Corporation

............................................... Publisher: Prentice Hall Pub Date: October 13, 2006 Print ISBN-10: 0-13-239077-9 Print ISBN-13: 978-0-13-239077-4 Pages: 880

  

The New State-of-the-Art in Information Security: Now Covers the Economics of

Cyber Security and the Intersection of Privacy and Information Security For years, IT and security professionals and students have turned to Security in Computing as the definitive guide to information about computer security attacks and countermeasures. In their new fourth edition, Charles P. Pfleeger and Shari Lawrence Pfleeger have thoroughly updated their classic guide to reflect today's newest technologies, standards, and trends. The authors first introduce the core concepts and vocabulary of computer security,

including attacks and controls. Next, the authors systematically identify and assess threats

now facing programs, operating systems, database systems, and networks. For each threat, they offer best-practice responses.

  Security in Computing, Fourth Edition, goes beyond technology, covering crucial management issues faced in protecting infrastructure and information. This edition

contains an all-new chapter on the economics of cybersecurity, explaining ways to make a

business case for security investments. Another new chapter addresses privacy--from data

mining and identity theft, to RFID and e-voting.

  New coverage also includes Programming mistakes that compromise security: man-in-the-middle, timing, and privilege escalation attacks Web application threats and vulnerabilities Networks of compromised systems: bots, botnets, and drones Rootkits--including the notorious Sony XCP

  New malicious code attacks, including false interfaces and keystroke loggers

Improving code quality: software engineering, testing, and liability approaches

Biometric authentication: capabilities and limitations Using the Advanced Encryption System (AES) more effectively

Balancing dissemination with piracy control in music and other digital content

Countering new cryptanalytic attacks against RSA, DES, and SHA Responding to the emergence of organized attacker groups pursuing profit

  

Security in Computing, Fourth Edition

By Charles P. Pfleeger - Pfleeger Consulting Group, Shari Lawrence Pfleeger - RAND Corporation

...............................................

Publisher: Prentice Hall Pub Date: October 13, 2006 Print ISBN-10: 0-13-239077-9 Print ISBN-13: 978-0-13-239077-4 Pages: 880

  

  

  

  

  

  

  

  

  Copyright

  Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed with initial capital letters or in all capitals. The authors and publisher have taken care in the preparation of this book, but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of the use of the information or programs contained herein.

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  Library of Congress Cataloging-in-Publication Data

  Pfleeger, Charles P., 1948- Security in computing / Charles P. Pfleeger, Shari Lawrence Pfleeger. 4th ed. p. cm. Includes bibliographical references and index.

  ISBN 0-13-239077-9 (hardback : alk. paper)

  1. Computer security. 2. Data protection. 3. Privacy, Right of. I. Pfleeger, Shari Lawrence. II. Title. QA76.9.A25P45 2006 005.8dc22 2006026798 Copyright © 2007 Pearson Education, Inc.

  All rights reserved. Printed in the United States of America. This publication is protected by copyright, and permission must be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permissions, write to: Pearson Education, Inc.

  Rights and Contracts Department One Lake Street Upper Saddle River, NJ 07458 Fax: (201) 236-3290 Text printed in the United States on recycled paper at Courier in Westford, Massachusetts.

  First printing, October 2006

  Foreword

  In the 1950s and 1960s, the prominent conference gathering places for practitioners and users of computer technology were the twice yearly Joint Computer Conferences (JCCs)initially called the Eastern and Western JCCs, but later renamed the Spring and Fall JCCs and even later, the annual National (AFIPS) Computer Conference. From this milieu, the topic of computer securitylater to be called information system security and currently also referred to as "protection of the national information infrastructure"moved from the world of classified defense interests into public view. A few peopleRobert L. Patrick, John P. Haverty, and I among othersall then at the RAND Corporationhad been talking about the growing dependence of the country and its institutions on computer technology. It concerned us that the installed systems might not be able to protect themselves and their data against intrusive and destructive attacks. We decided that it was time to bring the security aspect of computer systems to the attention of the technology and user communities.

  The enabling event was the development within the National Security Agency (NSA) of a remote-access time-sharing system with a full set of security access controls, running on a Univac 494 machine, and serving terminals and users not only within the headquarters building at Fort George G. Meade, Maryland, but also worldwide. Fortuitously, I knew details of the system.

  Persuading two others from RAND to helpDr. Harold Peterson and Dr. Rein Turnplus Bernard Peters of NSA, I organized a group of papers and presented it to the SJCC conference management as a ready-made additional paper session to be chaired by me. [1] The conference accepted the offer, and the session was presented at the Atlantic City (NJ) Convention Hall

  Soon thereafter and driven by a request from a defense contractor to include both defense classified and business applications concurrently in a single mainframe machine functioning in a remote-access mode, the Department of Defense, acting through the Advanced Research Projects Agency (ARPA) and later the Defense Science Board (DSB), organized a committee, which I chaired, to study the issue of security controls for computer systems. The intent was to produce a document that could be the basis for formulating a DoD policy position on the matter. The report of the committee was initially published as a classified document and was formally presented to the sponsor (the DSB) in January 1970. It was later declassified and republished (by the RAND Corporation) in October 1979. [2] It was widely circulated and became nicknamed "the Ware report." The report and a historical introduction are available on the RAND web site. [3] Subsequently, the United States Air Force (USAF) sponsored another committee chaired by James P. Anderson. [4] Its report, published in 1972, recommended a 6-year R&D security program totaling some $8M. [5] The USAF responded and funded several projects, three of which were to design and implement an operating system with security controls for a specific computer. Eventually these activities led to the "Criteria and Evaluation" program sponsored by the NSA. It culminated in the "Orange Book" [6] in 1983 and subsequently its supporting array of documents, which were nicknamed "the rainbow series." [7] Later, in the 1980s and on into the 1990s, the subject became an international one leading to the ISO standard known as the "Common Criteria." [8] It is important to understand the context in which system security was studied in the early decades. The defense information in document form. It had evolved a very elaborate scheme for compartmenting material into groups, sub-groups and super-groups, each requiring a specific personnel clearance and need-to-know as the basis for access. [9] It also had a centuries-long legacy of encryption technology and experience for protecting classified information in transit. Finally, it understood the personnel problem and the need to establish the trustworthiness of its people. And it certainly understood the physical security matter. Thus, "the" computer security issue, as it was understood in the 1960s and even later, was how to create in a computer system a group of access controls that would implement or emulate the processes of the prior paper world, plus the associated issues of protecting such software against unauthorized change, subversion, and illicit use, and of embedding the entire system in a secure physical environment with appropriate management oversights and operational doctrine and procedures. The poorly understood aspect of security was primarily the software issue with, however, a collateral hardware aspect; namely, the risk that it might malfunctionor be penetratedand subvert the proper behavior of software. For the related aspects of communications, personnel, and physical security, there was a plethora of rules, regulations, doctrine, and experience to cover them. It was largely a matter of merging all of it with the hardware/software aspects to yield an overall secure system and operating environment.

  However, the world has now changed in essential ways. The desktop computer and workstation have appeared and proliferated widely. The Internet is flourishing and the reality of a World Wide Web is in place. Networking has exploded and communication among computer systems is the rule, not the exception. Many commercial transactions are now web-based; many commercial communitiesthe financial one in particularhave moved into a web posture. The "user" of any computer system can literally be anyone in the world.

  Networking among computer systems is ubiquitous; informationsystem outreach is the goal. The net effect of all of this has been to expose the computer- based information systemits hardware, its software, its software processes, its databases, its communicationsto an environment over which no onenot end-user, not network administrator or system owner, not even governmenthas control. What must be done is to provide appropriate technical, procedural, operational, and environmental safeguards against threats as they might appear or be imagined, embedded in a societally acceptable legal framework. And appear threats didfrom individuals and organizations, national and international. The motivations to penetrate systems for evil purpose or to create malicious softwaregenerally with an offensive or damaging consequencevary from personal intellectual satisfaction to espionage, to financial reward, to revenge, to civil disobedience, and to other reasons. Information-system security has moved from a largely self-contained bounded environment interacting with a generally known and disciplined user community to one of worldwide scope with a body of users that may not be known and are not necessarily trusted. Importantly, security controls now must deal with circumstances over which there is largely no control or expectation of avoiding their impact. Computer security, as it has evolved, shares a similarity with liability insurance; they each face a threat environment that is known in a very general way and can generate attacks over a broad spectrum of possibilities; but the exact details or even time or certainty of an attack is unknown until an event has occurred. On the other hand, the modern world thrives on information and its flows; the contemporary world, society, and institutions cannot function without their computer-communication-based information systems. Hence, these systems must be protected in all dimensionstechnical, procedural, operational, responsible for protecting the organization's information assets. Progress has been slow, in large part because the threat has not been perceived as real or as damaging enough; but also in part because the perceived cost of comprehensive information system security is seen as too high compared to the risksespecially the financial consequencesof not doing it. Managements, whose support with appropriate funding is essential, have been slow to be convinced.

  This book addresses the broad sweep of issues above: the nature of the threat and system vulnerabilities (

Chapter 1 );

  cryptography and

   ); the Common Criteria

  (

   );

  managing risk

  ;

  and legal, ethical, and privacy issues

   ). The

  book also describes security controls that are currently available such as encryption protocols, software development practices, firewalls, and intrusion-detection systems. Overall, this book provides a broad and sound foundation for the information- system specialist who is charged with planning and/or organizing and/or managing and/or implementing a comprehensive information-system security program. Yet to be solved are many technical aspects of information securityR&D for hardware, software, systems, and architecture; and the corresponding products. Notwithstanding, technology per se is not the long pole in the tent of progress. Organizational and management motivation and commitment to get the security job done is. Today, the collective information infrastructure of the country and of the world is slowly moving up the learning curve; every mischievous or malicious event helps to push it along. The terrorism-based events of recent times are helping to drive it. Is it far enough up the curve to have reached an appropriate balance between system safety and threat? Almost certainly, the answer is, "No, not yet; there is a long way to go." [10]

  Willis H. Ware The RAND Corporation Santa Monica, California Citations 1. "Security and Privacy in Computer Systems," Willis H.

  Ware; RAND, Santa Monica, CA; P-3544, April 1967. Also published in Proceedings of the 1967 Spring Joint Computer Conference (later renamed to AFIPS Conference Proceedings), pp 279 seq, Vol. 30, 1967.

  "Security Considerations in a Multi-Programmed Computer System," Bernard Peters; Proceedings of the 1967 Spring Joint Computer Conference (later renamed to AFIPS Conference Proceedings), pp 283 seq, vol 30, 1967.

  "Practical Solutions to the Privacy Problem," Willis H. Ware; RAND, Santa Monica, CA; P-3544, April 1967. Also published in Proceedings of the 1967 Spring Joint Computer Conference (later renamed to AFIPS Conference Proceedings), pp 301 seq, Vol. 30, 1967.

  "System Implications of Information Privacy," Harold E. Peterson and Rein Turn; RAND, Santa Monica, CA; P-3504, April 1967. Also published in Proceedings of the 1967 Spring Joint Computer Conference (later renamed to AFIPS Conference Proceedings), pp 305 seq, vol. 30, 1967.

  2. "Security Controls for Computer Systems," (Report of the

  Defense Science Board Task Force on Computer Security), RAND, R-609-1-PR. Initially published in January 1970 as a classified document. Subsequently, declassified and republished October 1979.

  "Security Controls for Computer Systems"; R-609.1, RAND, 1979

   Historical

  setting for R-609.1 4. "Computer Security Technology Planning Study," James P. Anderson; ESD-TR-73-51, ESD/AFSC, Hanscom AFB, Bedford, MA; October 1972.

  5. All of these documents are cited in the bibliography of this

  book. For images of these historical papers on a CDROM, see the "History of Computer Security Project, Early Papers

  Part 1," Professor Matt Bishop; Department of Computer Science, University of California at Davis.

   6. "DoD Trusted Computer System Evaluation Criteria," DoD

  Computer Security Center, National Security Agency, Ft George G. Meade, Maryland; CSC-STD-001-83; Aug 15, 1983.

  

7. So named because the cover of each document in the series

  had a unique and distinctively colored cover page. For example, the "Red Book" is "Trusted Network Interpretation," National Computer Security Center, National Security Agency, Ft. George G. Meade, Maryland; NCSC-TG- 005, July 31, 1987. USGPO Stock number 008-000-00486- 2.

  

8. "A Retrospective on the Criteria Movement," Willis H. Ware;

RAND, Santa Monica, CA; P-7949, 1995.

  Preface

  Every day, the news media give more and more visibility to the effects of computer security on our daily lives. For example, on a single day in June 2006, the Washington Post included three important articles about security. On the front page, one article discussed the loss of a laptop computer containing personal data on 26.5 million veterans. A second article, on the front page of the business section, described Microsoft's new product suite to combat malicious code, spying, and unsecured vulnerabilities in its operating system. Further back, a third article reported on a major consumer electronics retailer that inadvertently installed software on its customers' computers, making them part of a web of compromised slave computers. The sad fact is that news like this appears almost every day, and has done so for a number of years. There is no end in sight.

  Even though the language of computer securityterms such as virus, Trojan horse, phishing, spywareis common, the application of solutions to computer security problems is uncommon. Moreover, new attacks are clever applications of old problems. The pressure to get a new product or new release to market still in many cases overrides security requirements for careful study of potential vulnerabilities and countermeasures. Finally, many people are in denial, blissfully ignoring the serious harm that insecure computing can cause.

  Why Read This Book?

  Admit it. You know computing entails serious risks to the privacy and 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 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 the same knowledge and experience with respect to the risks of secure computing. How do you control the risk of computer security? Learn about the threats to computer security.

  Understand what causes these threats by studying how vulnerabilities arise in the development and use of computer systems. Survey the controls that can reduce or block these threats. Develop a computing styleas a user, developer, manager, consumer, and voterthat balances security and risk.

  The field of computer security changes rapidly, but the underlying problems remain largely unchanged. In this book you will find a progression that shows you how current complex attacks are often instances of more fundamental concepts.

  Users and Uses of This Book

  This book is intended for the study of computer security. Many of you want to study this topic: college and university students, computing professionals, managers, and users of all kinds of computer-based systems. All want to know the same thing: in how much information you need about particular topics: Some 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. The chapters of this book progress in an orderly manner, from general security concerns to the particular needs of specialized applications, and finally to overarching management and legal issues. Thus, the book covers five key areas of interest:

  introduction: threats, vulnerabilities, and controls encryption: the "Swiss army knife" of security controls code: security in programs, including applications, operating

  systems, database management systems, and networks

  management: building and administering a computing

  installation, from one computer to thousands, and understanding the economics of cybersecurity

  

law, privacy, ethics: non-technical approaches by which

  society controls computer security risks These areas are not equal in size; for example, more than half the book is devoted to code because so much of the risk is at least partly caused by program code that executes on computers.

  The first chapter introduces the concepts and basic vocabulary of computer security. Studying the second chapter provides an understanding of what encryption is and how it can be used or design or build a car,

  cover successively larger pieces of

  software: individual programs, operating systems, complex applications like database management systems, and finally networks, which are distributed complex systems.

  

  discusses managing and administering security, and describes how to find an acceptable balance between threats and controls.

  addresses an important management issue

  by exploring the economics of cybersecurity: understanding and communicating the costs and benefits. In

  we turn to

  the personal side of computer security as we consider how security, or its lack, affects personal privacy.

  covers

  the way society at large addresses computer security, through its laws and ethical systems. Finally,

  returns to

  cryptography, this time to look at the details of the encryption algorithms themselves. Within that organization, you can move about, picking and choosing topics of particular interest. Everyone should read

   to build a vocabulary and a foundation. It is wise to

  read

  

because cryptography appears in so many

  different control techniques. Although there is a general progression from small programs to large and complex networks, you can in fact read

   out of

  sequence or pick topics of greatest interest.

  

  may be just right for the professional looking for non-technical controls to complement the technical ones of the earlier chapters. These chapters may also be important for the computer science student who wants to look beyond a narrow view of bytes and protocols. We recommend and

   for everyone, because those chapters deal with the human

  aspects of security: privacy, laws, and ethics. All computing is ultimately done to benefit humans, and so we present personal risks and approaches to computing.

  is for people

  who want to understand some of the underlying mathematics

  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 computer science 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 fourth edition of Security in Computing, first published in 1989. Since then, the specific threats, vulnerabilities, and controls have changed, even though many of the basic notions have remained the same.

  The two changes most obvious to people familiar with the previous editions are the additions of two new chapters, on the economics of cybersecurity and privacy. These two areas are receiving more attention both in the computer security community and in the rest of the user population. But this revision touched every existing chapter as well. The still since the previous edition in 2003, and so we present new information on threats and controls of many types. Change include: the shift from individual hackers working for personal reasons to organized attacker groups working for financial gain programming flaws leading to security failures, highlighting man-in-the-middle, timing, and privilege escalation errors recent malicious code attacks, such as false interfaces and keystroke loggers approaches to code quality, including software engineering, testing, and liability approaches rootkits, including ones from unexpected sources web applications' threats and vulnerabilities privacy issues in data mining WiFi network security cryptanalytic attacks on popular algorithms, such as RSA, DES, and SHA, and recommendations for more secure use of these bots, botnets, and drones, making up networks of compromised systems update to the Advanced Encryption System (AES) with experience from its first several years of its use

the divide between sound authentication approaches and users' actions biometric authentication capabilities and limitations the conflict between efficient production and use of digital content (e.g., music and videos) and control of piracy

  In addition to these major changes, there are numerous small corrective and clarifying ones, ranging from wording and notational changes for pedagogic reasons to replacement, deletion, rearrangement, and expansion of sections.

  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 as they have influenced this book. 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. In particular, we are grateful to the RAND Corporation for permission to present material about its Vulnerability, Assessment and Mitigation method and to use its government e-mail analysis as a case study in

Chapter 8 . Second, 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, and Cable & Wireless. If you worked with us at any of these locations, chances are high that you had some impact on this book. And for all the side conversations, debates, arguments, and light moments, we are grateful. For this fourth edition, Roland Trope and Richard Gida gave us particularly helpful suggestions for

  

  Authors are the products of their environments. We write to educate because we had good educations ourselves, and because we think the best response to a good education is to pass it along to others. Our parents, Paul and Emma Pfleeger and Emanuel and Beatrice Lawrence, were critical in supporting us and encouraging us to get the best educations we could. Along the way, certain teachers gave us gifts through their teaching. Robert L. Wilson taught Chuck how to learn about computers, and Libuse L. Reed taught him how to write about them. Florence Rogart, Nicholas Sterling and Mildred Nadler taught Shari how to analyze and probe. To all these people, we express our sincere thanks.

  Charles P. Pfleeger Shari Lawrence Pfleeger Washington, D.C.

Chapter 1. Is There a Security Problem in Computing? In this chapter The risks involved in computing The goals of secure computing: confidentiality, integrity, availability The threats to security in computing: interception, interruption, modification,

  fabrication

Controls available to address these threats: encryption, programming controls,

operating systems, network controls, administrative controls, law, and ethics

1.1. What Does "Secure" Mean?

  How do we protect our most valuable assets? One option is to place them in a safe place, like a bank. We seldom hear of a bank robbery these days, even though it was once a fairly lucrative undertaking. In the American Wild West, banks kept large amounts of cash on hand, as well as gold and silver, which could not be traced easily. In those days, cash was much more commonly used than checks. Communications and transportation were primitive enough that it might have been hours before the legal authorities were informed of a robbery and days before they could actually arrive at the scene of the crime, by which time the robbers were long gone. To control the situation, a single guard for the night was only marginally effective. Should you have wanted to commit a robbery, you might have needed only a little common sense and perhaps several days to analyze the situation; you certainly did not require much sophisticated training. Indeed, you usually learned on the job, assisting other robbers in a form of apprenticeship. On balance, all these factors tipped very much in the favor of the criminal, so bank robbery was, for a time, considered to be a profitable business. Protecting assets was difficult and not always effective. Today, however, asset protection is easier, with many factors working against the potential criminal. Very sophisticated alarm and camera systems silently protect secure places like banks whether people are around or not. The techniques of criminal investigation have become so effective that a person can be identified by genetic material (DNA), fingerprints, retinal patterns, voice, a composite sketch, ballistics evidence, or other hard-to-mask characteristics. The assets are stored in a safer form. For instance, many bank branches now contain less cash than some large retail stores because much of a bank's business is conducted with checks, electronic transfers, credit cards, or debit cards. Sites that must store large amounts of cash or currency are protected with many levels of security: several layers of physical systems, complex locks, multiple- party systems requiring the agreement of several people to allow access, and other schemes. Significant improvements in transportation and communication mean that police can be at the scene of a crime in minutes; dispatchers can alert other officers in seconds about the suspects to watch for. From the criminal's point of view, the risk and required sophistication are so high that there are usually easier ways than bank robbery to make money.

  Protecting Valuables

  This book is about protecting our computer-related assets, not about protecting our money and gold bullion. That is, we plan to discuss security for computing systems, not banks. But we can learn from our analysis of banks because they tell us some general principles about protection. In other words, when we think about protecting valuable information, we can learn a lot from the way we have protected other valuables in the past. For example, presents the differences between how people protect computing systems and how banks protect money. The table reinforces the point that we have many challenges to address when protecting computers and data, but the nature of the challenges may mean that we need different and more effective approaches than we have used in the past.

  Table 1-1. Protecting Money vs. Protecting Information. Characteristic Bank Protecting People Protecting Information Money Size and Sites storing money are Items storing valuable assets are portability large, unwieldy, not at very small and portable. The

all portable. Buildings physical devices in computing can require guards, vaults, be so small that thousands of security to protect fit comfortably in a briefcase. money.

  Ability to avoid Difficult. When banks Simple. When information is physical deal with physical handled electronically, no physical contact currency, a criminal contact is necessary. Indeed, when

must physically demand banks handle money electronically,

the money and carry it almost all transactions can be done

away from the bank's without any physical contact. Money premises. can be transferred through computers, mail, or telephone.

  Value of assets Very high. Variable, from very high to very low. Some information, such as medical history, tax payments, investments, or educational background, is confidential. Other information, about troop movements, sales strategies, buying patterns, can be very sensitive. Still other information, such as address and phone number, may be of no consequence and easily accessible by other means.

  Protecting our valuables, whether they are expressed as information or in some other way, ranges from quite unsophisticated to very sophisticated. We can think of the Wild West days as an example of the "unsophisticated" end of the security spectrum. And even today, when we have more sophisticated means of protection than ever before, we still see a wide range in how people and businesses actually use the protections available to them. In fact, we can find far too many examples of computer security that seem to be back in the Wild West days. Although some organizations recognize computers and their data as valuable and vulnerable resources and have applied appropriate protection, others are dangerously deficient in their security measures. In some cases, the situation is even worse than that do not even recognize that their resources should be controlled and protected. And as software consumers, we find that the lack of protection is all the more dangerous when we are not even aware that we are susceptible to software piracy or corruption.

  Sidebar 1-1: Protecting Software in Automobile Control Systems The amount of software installed in an automobile grows larger from year to

year. Most cars, especially more expensive ones, use dozens of microcontrollers

to provide a variety of features to entice buyers. There is enough variation in microcontroller range and function that the Society of Automotive Engineers

(Warrendale, Pennsylvania) has set standards for the U.S. automotive industry's

software. Software in the microcontrollers ranges through three classes:

low speed (class Aless than 10 kb per second) for convenience features,

such as radios medium speed (class B10 to 125 kb per second) for the general transfer of information, such as that related to emissions, speed, or instrumentation

high speed (class Cmore than 125 kb per second) for real-time control,

such as the power train or a brake-by-wire system

  

These digital cars use software to control individual subsystems, and then more software to connect the systems in a network .

However, the engineers designing and implementing this software see no reason

to protect it from hackers. Whitehorn-Umphres reports that, from the engineers'

point of view, the software is too complicated to be understood by a hacker. "And even if they could [understand it], they wouldn't want to."

Whitehorn-Umphres points out a major difference in thinking between hardware designers and software designers. "As hardware engineers, they assumed that,

perhaps aside from bolt-on aftermarket parts, everything else is and should be a black box." But software folks have a different take: "As a software designer, I assume that all digital technologies are fair game for being played with. . . . it takes a special kind of personality to look at a software-enabled device and see the potential for manipulation and changea hacker personality." He points out that hot-rodders and auto enthusiasts have a long history of

tinkering and tailoring to make specialized changes to mass-produced cars. And the unprotected software beckons them to continue the tradition. For instance, there are reports of recalibrating the speedometer of two types of Japanese motorcycles to fool the bike about how fast it is really going (and thereby

enabling faster-than-legal speeds). Whitehorn-Umphres speculates that soon you

will be able to "download new ignition mappings from your PC. The next step will be to port the PC software to handheld computers so as to make on-the-road modifications that much easier." The possibility of crime is bad enough. But worse yet, in the event of a crime, some organizations neither investigate nor prosecute for fear that the revelation will damage their public image. For example, would you feel safe depositing your money in a bank that had just suffered a several million-dollar loss through computer-related embezzlement? In fact, the breach of security makes that bank painfully aware of all its security weaknesses. Once bitten, twice shy; after the loss, the bank will probably enhance its security substantially, quickly becoming safer than a bank that had not been recently victimized.

  Even when organizations want to take action against criminal activity, criminal investigation and prosecution can be hindered by statutes that do not recognize electromagnetic signals as property. The news media sometimes portrays computer intrusion by teenagers as a prank no more serious than tipping over an outhouse. But, as we see in later chapters, computer intrusion can hurt businesses and even take lives. The legal systems around the world are rapidly coming to grips with the nature of electronic property as intellectual property critical to organizational or mission success; laws are being implemented and court decisions declared that acknowledge the value of information stored or transmitted via computers. But this area is still new to many courts, and few precedents have been established.

  Throughout this book, we look at examples of how computer security affects our livesdirectly and indirectly. And we examine techniques to prevent security breaches or at least to mitigate their effects. We address the security concerns of software practitioners as well as those professionals, managers, and users whose products, services, and well-being depend on the proper functioning of computer systems. By studying this book, you can develop an understanding of the basic problems with them. In particular, we do the following: examine the risks of security in computing consider available countermeasures or controls stimulate thought about uncovered vulnerabilities identify areas where more work is needed

  In this chapter, we begin by examining what kinds of vulnerabilities computing systems are prone to. We then consider why these vulnerabilities are exploited: the different kinds of attacks that are possible. This chapter's third focus is on who is involved: the kinds of people who contribute to the security problem. Finally, we introduce how to prevent possible attacks on systems.

  Characteristics of Computer Intrusion Any part of a computing system can be the target of a crime.

  When we refer to a computing system, we mean a collection of hardware, software, storage media, data, and people that an organization uses to perform computing tasks. Sometimes, we assume that parts of a computing system are not valuable to an outsider, but often we are mistaken. For instance, we tend to think that the most valuable property in a bank is the cash, gold, or silver in the vault. But in fact the customer information in the bank's computer may be far more valuable. Stored on paper, recorded on a storage medium, resident in memory, or transmitted over telephone lines or make money illicitly. A competing bank can use this information to steal clients or even to disrupt service and discredit the bank. An unscrupulous individual could move money from one account to another without the owner's permission. A group of con artists could contact large depositors and convince them to invest in fraudulent schemes. The variety of targets and attacks makes computer security very difficult.

  [1] In this book, boldface identifies new terms being introduced.

  Any system is most vulnerable at its weakest point. A robber intent on stealing something from your house will not attempt to penetrate a two-inch-thick metal door if a window gives easier access. Similarly, a sophisticated perimeter physical security system does not compensate for unguarded access by means of a simple telephone line and a modem. We can codify this idea as one of the principles of computer security.

  Principle of Easiest Penetration: An intruder must be

  expected to use any available means of penetration. The penetration may not necessarily be by the most obvious means, nor is it necessarily the one against which the most solid defense has been installed. And it certainly does not have to be the way we want the attacker to behave.

  This principle implies that computer security specialists must consider all possible means of penetration. Moreover, the penetration analysis must be done repeatedly, and especially whenever the system and its security change. People sometimes underestimate the determination or creativity of attackers. Remember that computer security is a game with rules only for the defending team: The attackers can (and will) use any means they can. Perhaps the hardest thing for people outside the security community to do is to think like the attacker. One group of creative security researchers investigated a wireless security system and reported a vulnerability to the system's chief designer, who replied "that would work, but no attacker would try it" Don't believe that for a minute: No attack is out of bounds.

  Strengthening one aspect of a system may simply make another means of penetration more appealing to intruders. For this reason, let us look at the various ways by which a system can be breached.

1.2. Attacks

  When you test any computer system, one of your jobs is to imagine how the system could malfunction. Then, you improve the system's design so that the system can withstand any of the problems you have identified. In the same way, we analyze a system from a security perspective, thinking about ways in which the system's security can malfunction and diminish the value of its assets.

  Vulnerabilities, Threats, Attacks, and Controls

  A computer-based system has three separate but valuable components: hardware, software, and data. Each of these assets offers value to different members of the community affected by the system. To analyze security, we can brainstorm about the ways in which the system or its information can experience some kind of loss or harm. For example, we can identify data whose format or contents should be protected in some way. We want our security system to make sure that no data are disclosed to unauthorized parties. Neither do we want the data to be modified in illegitimate ways. At the same time, we must ensure that legitimate users have access to the data. In this way, we can identify weaknesses in the system. A vulnerability is a weakness in the security system, for example, in procedures, design, or implementation, that might be exploited to cause loss or harm. For instance, a particular system may be vulnerable to unauthorized data manipulation because the system does not verify a user's identity before allowing data access.

  A threat to a computing system is a set of circumstances that between a threat and a vulnerability, consider the illustration in

  

Here, a wall is holding water back. The water to the

  left of the wall is a threat to the man on the right of the wall: The water could rise, overflowing onto the man, or it could stay beneath the height of the wall, causing the wall to collapse. So the threat of harm is the potential for the man to get wet, get hurt, or be drowned. For now, the wall is intact, so the threat to the man is unrealized.

  

Figure 1-1. Threats, Controls, and Vulnerabilities.

  However, we can see a small crack in the walla vulnerability that threatens the man's security. If the water rises to or beyond the level of the crack, it will exploit the vulnerability and harm the man.