The Right to Privacy 29
The Expert Witness 31
Chapter Review 32
Chapter Exercises 32
References 33
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3 Search Warrants and Subpoenas 35 Distinguishing between Warrants and Subpoenas 36
What Is a Search and When Is It Legal? 37
Basic Elements of Obtaining a Warrant 40
The Plain View Doctrine 43
The Warrantless Search 44
Subpoenas 50
Chapter Review 51
Chapter Exercises 52
References 52
4 Legislated Privacy Concerns 55 General Privacy 56
Financial Legislation 59
Privacy in Health Care and Education 62
Privileged Information 64
Chapter Review 67
Chapter Exercises 68
References 68
5 The Admissibility of Evidence 71 What Makes Evidence Admissible? 71
Keeping Evidence Authentic 76
Defining the Scope of the Search 84
When the Constitution Doesn’t Apply 84
Chapter Review 89
Chapter Exercises 89
References 89
6 First Response and the Digital Investigator 91 Forensics and Computer Science 91
Controlling the Scene of the Crime 96
Handling Evidence 100
Chapter Review 109
Chapter Exercises 109
References 110
Contents
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7 Data Acquisition 111 Order of Volatility 112
Memory and Running Processes 112
Acquiring Media 121
Chapter Review 128
Chapter Exercises 128
References 129
8 Finding Lost Files 131 File Recovery 131
The Deleted File 141
Data Carving 145
Chapter Review 149
Chapter Exercises 150
References 150
9 Document Analysis 151 File Identification 151
Understanding Metadata 157
Mining the Temporary Files 172
Identifying Alternate Hiding Places of Data 176
Chapter Review 183
Chapter Exercises 183
References 183
10 E-mail Forensics 185 E-mail Technology 185
Information Stores 191
The Anatomy of an E-mail 196
An Approach to E-mail Analysis 203
Chapter Review 210
Chapter Exercises 211
References 211
Contents
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Contents
11 Web Forensics 213 Internet Addresses 213
Web Browsers 215
Web Servers 233
Proxy Servers 238
Chapter Review 244
Chapter Exercises 244
References 245
12 Searching the Network 247 An Eagle’s Eye View 247
Initial Response 248
Proactive Collection of Evidence 250
Post-Incident Collection of Evidence 262
Router and Switch Forensics 268
Chapter Review 275
Chapter Exercises 275
References 276
13 Excavating a Cloud 277 What Is Cloud Computing? 277
Shaping the Cloud 279
The Implications of Cloud Forensics 284
On Virtualization 291
Constitutional Issues 300
Chapter Review 303
Chapter Exercises 304
References 304
14 Mobile Device Forensics 307 Challenges of Mobile Device Forensics 307
How Cell Phones Work 308
Data Storage on Cell Phones 313
Acquisition and Storage 317
Legal Aspects of Mobile Device Forensics 322
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Contents
Chapter Review 324
Chapter Exercises 325
References 325
15 Fighting Antiforensics 327 Artifact Destruction 328
Hiding Data on the System 336
Covert Data 347
Chapter Review 354
Chapter Exercises 355
References 355
16 Litigation and Electronic Discovery 357 What Is E-Discovery? 358
A Roadmap of E-Discovery 358
Conclusion 377
Chapter Review 377
Chapter Exercises 377
References 378
17 Case Management and Report Writing 379 Managing a Case 379
Writing Reports 389
Chapter Review 393
Chapter Exercises 394
References 394
18 Tools of the Digital Investigator 395 Software Tools 395
Working with “Court-Approved” Tools 410
Hardware Tools 413
Nontechnical Tools 418
Chapter Review 421
Chapter Exercises 422
References 422
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Contents
19 Building a Forensic Workstation 423 What Is a Forensic Workstation? 424
Commercially Available Forensic Workstations 425
Building a Forensic Workstation From Scratch 429
Chapter Review 440
Chapter Exercises 440
References 440
20 Licensing and Certification 441 Digital Forensic Certification 441
Vendor-Neutral Certification Programs 442
Vendor-Specific Certification Programs 449
Digital Forensic Licensing Requirements 452
Chapter Review 454
Chapter Exercises 454
References 454
21 The Business of Digital Forensics 457 Starting a New Forensics Organization 458
Maintaining the Organization 466
Generating Revenue 478
Organizational Certification 481
Chapter Review 483
Chapter Exercises 483
References 483
A Chapter Review Answers 485
B Sample Forms 505
Glossary 511
Index 521
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Pr e fAc e
In performing an investigation that explores the use of computers or digital data, one is basically embarking on an archaeological expedition. To extract useful artifacts (information, in our case), one must be exceedingly careful in how one approaches the site. The similarities between a digital investigation and an archaeo- logical excavation are much closer than you might imagine. Data, like physical arti- facts, gets dropped into the oddest places. The effects of time and environment are just as damaging, if not more so, to digital artifacts as they are physical mementos.
Wh y Th i S Bo o k ?
Archaeologists are fully aware that, due to the passage of time, there are things they can never recover. The skin that once covered a skeleton long buried in the desert can never be found and analyzed. Likewise, data that was once stored in active memory on a computer can’t be recovered once the computer is switched off. However, in each example, it is possible to uncover evidence that both existed. When you first begin a digital investigation, you are undertaking a modern archaeological dig. Just like the shards of broken pots tell the anthropologist a lot about the culture that once used the vessel, the data you dig out of the computer can tell you volumes about the people who used the system.
This book takes the concepts of archaeology and applies them to computer science. It is a tutorial on how to investigate a computer system to find evidence of a crime or other misbehavior, and to make sure that evidence will stand up in
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Preface
court. While there are numerous other books that cover the whys and wherefores of digital forensics, this one will go into some detail on how to accomplish the task.
We’ve all watched the TV programs where the good guys figure out everything the bad guys did just from examining a piece of hair. (Is this why the bad guys are always called “hairballs”?) In modern-day investigations, the role of the computer plays as big a part as the star witness in many cases. In fact, the computer often is the star witness. Many cases have been solved or settled on the basis of what trained professionals were able to discover while examining electronic evidence (e-evidence).
However, the courts take a dim view on just anybody digging around in some- body else’s computers. They generally insist that legal process be followed, and that only a trained professional attempt the examination. The extraction and analysis of e-evidence is all part of what we call computer forensics. So what is forensics? The word itself originated from the Latin word forum, which described a place where people could assemble publicly and discuss matters of interest to the community. In that context, the word was derived from the strict rules of presentation applied to such discussions. In the context of this book, the word best means application of sci- ence or technology to the collection of evidence for the purpose of establishing facts. The vast majority of references specify that forensic science is targeted at criminal inves- tigation. However, in the real world, digital investigations are commonly used in civil cases and within organizations to identify members engaged in illicit activities.
A crime scene investigator might have DNA from samples of hair found at the scene analyzed to prove that a specific individual was on the scene at least once. Chemical analysis of soil can identify a geographical origin. The process of com- puter forensics is a series of steps by which professionals can prove the following:
• Data exists. • Data once existed. • Data originated from a specific source. • A particular individual either created or had access to the data in question. • The data is relevant to the case. • The data has not changed in any way from acquisition to analysis.
While it is not always necessary to prove all of the above statements are true, in order to secure a case it is best if as many as possible can be locked down. Even when all of the above are proven, a slick lawyer can always point out the fact that e-evidence is almost always circumstantial and press for reasons why the investigation team has presented insufficient corroborating evidence to demonstrate relevance or authentic- ity. (Both of these terms will be discussed in greater detail in the course of this book.) Even if you can prove beyond a shadow of a doubt that Tammy Sue created the letter
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