"Computer Forensics, Incident Response Essentials is a phenomenal introduction to the tools and techniques for computer forensic response. The book listed a number of tools that I had never heard of before. I can't wait to download several of these and take them for a spin."

--Stephen Northcutt, The SANS Institute

Submitted by Publisher, January, 2002

Preface

Billions of dollars are lost annually to crime, and computers are increasingly involved. It is clear that law enforcement agencies need to investigate digital evidence, but does it make sense to encourage a bunch of computer administrators to become junior g-men? Do we really need amateur digital sleuths? In a word, yes. Bad things are happening on computers and to computers, and the organizations responsible for these computers have a need to find out what exactly happened. You probably cannot pick up the phone and bring in law enforcement officials every time something anomalous happens on one of your servers and expect them to send out a team of forensic specialists, and even if you could, your corporate executives may not want that. All major corporations have internal security departments that are quite busy performing internal investigations. However, the security professionals who typically fill this role are accustomed to dealing with theft and safety issues and are often ill-prepared to deal with computer crime.

This book is inspired by the needs of the people who attend the author's seminars on computer forensics. If for no other reason than these sold-out seminars, we know that there is a big demand for greater expertise in digital investigations. System administrators and corporate security staff are the people we've designed the book for. Most of the seminar attendees are fairly skilled in the use and maintenance of Microsoft environments. Some of them are Unix specialists, but many students have expressed a strong desire to learn more about Unix. Once a corporation discovers that they know someone who can investigate Windows incidents, it is assumed that he or she knows everything about computers, and it is usually only a matter of time until this person is pressured into taking a look at a suspect Unix system.

Our students come from a wide variety of backgrounds and have diverse investigatory needs and desires. We try to accommodate these varying agendas in this book, to which we bring our experience in investigation and incident response. Warren Kruse is a former police officer who regularly performs computer forensic examinations inside and outside of Lucent Technologies. Jay Heiser is an information security consultant who has been on the response teams for numerous hacked Internet servers. To the maximum extent possible, this book contains everything useful that we've learned from performing investigations and teaching others to do so for themselves. We know what questions will be asked, and this book is designed to answer them. It is a practical guide to the techniques used by real people to investigate real computer crimes.

How to Read This Book

This book can be read cover to cover, as a complete introductory course in computer forensics. However, it is also meant to serve as a handbook, and we expect many readers to be familiar with some of the subjects we cover. For that reason, each chapter is a complete unit and can be read when convenient or necessary. You probably specialize in one or more of the areas covered in this text. However, we believe that the information presented in this book is at the minimum required level of legal and computer literacy, and we urge you to become knowledgeable in all of the areas we cover: legal, procedural, and technical.

A brief description of the information covered in each chapter is provided in the sections that follow.

Introduction to Computer Forensics

Chapter 1 outlines the basic process of evidence collection and analysis, which is the meat of computer forensics. Even those readers with a background in law enforcement will find new techniques in this chapter that are specific to computer forensics.

Tracking an Offender

The Internet is pervasive, and a high percentage of your investigations will involve either incoming or outgoing Internet traffic. The material in Chapter 2 will help you interpret the clues inside of email messages and news postings. It will also start you on the path toward becoming an Internet detective, using standard Internet services to perform remote investigations.

The Basics of Hard Drives and Storage Media

For the computer sleuth, hard drives are the most significant containers of evidence. Chapter 3 provides an understanding of both their logical and their physical configurations. It covers partitions and low-level formatting, filesystems, and hardware drive interfaces.

Encryption and Forensics

Cryptography has become ubiquitous in the virtual world of the Internet. A skilled investigator must have a solid understanding of the technology and goals of modern cryptography. It is relevant both in understanding evidence and, interestingly, in the preservation of evidence. Many investigators lack a necessary level of crypto-literacy, so Chapter 4 provides a broad introduction to encryption with special emphasis on its significance and application in computer forensics. We also discuss common encoding and archiving formats (such as uuencode and PKZIP) that can complicate your keyword searches. As digital signature technology grows in legal significance and finds new uses, forensic investigators will be expected to understand its limitations and must have a firm grasp of the ways in which a digital identity can be stolen. The digital timestamping of forensic evidence will soon become standard procedure in digital investigations. If you already have a background in these encryption concepts, then you may wish to skim this chapter.

Data Hiding

Being able to find hidden data is a crucial investigative skill. Even if you are highly crypto-literate, you still may not be aware of steganography (the art of hiding information by embedding covert messages within other messages) and other data-hiding techniques. Continuing the subject of encryption, Chapter 5 describes the use of specific password-cracking tools that we have successfully used during our investigations. This chapter categorizes and describes the ways that data can be hidden�not just by encryption�and provides practical guidance on how to find and read hidden data.

Hostile Code

Being able to identify and understand the implications of criminal tools is a skill that every investigator needs. Given that hostile code can be arcane and that few readers have a background in it, Chapter 6 provides an introduction to the topic and an overview of the types and capabilities of digital criminal tools that the investigator may encounter. We've included a couple of war stories involving the recent use of "hacker tools" on corporate PCs, which is becoming increasingly common.

Your Electronic Toolkit

Although forensic-specific tools have a certain James Bond�like appeal�and we cover these products�a large percentage of your work will be done with system tools that were not specifically created for the unique needs of forensic investigation. Chapter 7 will introduce you to a wide variety of utility types and specific brand name tools, along with instructions in their use in a digital investigation.

Investigating Windows Computers

Microsoft Windows, in all its various flavors, is the most widely used family of operating systems. While Chapter 8 assumes some background in Windows, you don't need to be a Microsoft Certified Systems Engineer in order to apply the techniques and tricks we discuss. Emphasis is placed on Windows NT 4.0 and Windows 9x, but several important new Windows 2000 features, such as the Encrypting File System, are covered. An experienced investigator soon learns that nothing is too obsolete to be in daily use somewhere, so the chapter concludes with Windows 3.1�specific material.

Introduction to Unix for Forensic Examiners

For those readers with no prior Unix experience, Chapter 9 provides an introduction with special emphasis on Unix characteristics that are most significant for the forensic investigator. Experienced Unix users can skim or skip this chapter.

Compromising a Unix Host

Chapter 10 is intended as background material for the investigation of hacked Internet hosts. It describes the process that Unix attackers typically use and provides an understanding of the goals of typical system hackers.

Investigating a Unix Host

While emphasizing the investigation of hacked Unix hosts, Chapter 11 describes techniques that are applicable to all forms of Unix investigation. It contains a detailed set of Unix-specific techniques and processes that use common Unix utilities for collecting and evaluating evidence. It also contains instructions on using a Unix boot CD to capture information over a network when you can't attach hardware directly to a suspect system.

Introduction to the Criminal Justice System

The final chapter explains what you need to do after you have begun collecting evidence and provides an overview of the criminal justice process. Legal concepts such as affidavits, subpoenas, and warrants are described. You will be a more effective interface between your organization and law enforcement agents if you understand what they do and how both investigations and prosecutions are structured by the legal system.

Appendixes

As in most books, the appendixes in this one contain information that doesn't fit neatly anywhere else. They are standalone guides to specific needs.

Appendix A, Internet Data Center Response Plan, defines a process for handling computer security incidents in Internet Data Centers.

Appendix B, Incident Response Triage, provides a list of general questions that should be asked during the investigation of a computer crime incident.

Appendix C, How to Become a Unix Guru, provides self-study suggestions for forensic examiners who want to improve their ability to investigate Unix hosts.

Appendix D, Exporting a Windows 2000 Personal Certificate, graphically depicts the process of exporting a Personal Certificate from a Windows 2000 computer. Investigators should practice this process to prepare themselves for incidents involving the Encrypted File System.

Appendix E, How to Crowbar Unix Hosts, describes the process of gaining administrative access to a Unix system by booting it from a floppy or CD.

Appendix F, Creating a Linux Boot CD, provides several suggestions on techniques and technology sources that are useful in the creation of bootable

Just as regular police forensics focus on the information available at a crime scene, computer forensics looks at evidence that can be gleaned in the aftermath of a computer security incident. Two computer security professionals provide a methodology for collecting information that can lead to a perpetrator and prove useful in prosecutions. Chapters cover encryption, data hiding, hostile code, and introductions to forensics on Windows and Unix operating systems.

Preface.
Acknowledgments.
1. Introduction to Computer Forensics.
2. Tracking an Offender.
3. The Basics of Hard Drives and Storage.
4. Encryption and Forensics.
5. Data Hiding.
6. Hostile Code.
7. Your Electronic Toolkit.
8. Investigating Windows Computers.
9. Introduction to Unix for Forensic Examiners.
10. Compromising a Unix Host.
11. Investigating a Unix Host.
12. Introduction to the Criminal Justice System.
13. Conclusion.

Appendix A. Internet Data Center Response Plan.
Appendix B. Incident Response Triage Questionnaire.
Appendix C. How to Become a Unix Guru.
Appendix D. Exporting a Windows 2000 Personal Certificate.
Appendix E. How to Crowbar Unix Hosts.
Appendix F. Creating a Linux Boot CD.
Appendix G. Contents of a Forensic CD.
Annotated Bibliography.
Index.