The Basics of Digital Forensics

The Primer for Getting Started in Digital Forensics

John Sammons

• Publisher: Syngress
• Year: 2012
• ISBN:
  9781597496629
• Topic: Computer Science
• Subtopic: Cyber Security
• Index: Computer Science

The Basics of Digital Forensics provides a foundation for people new to the field of digital forensics. This book teaches you how to conduct examinations by explaining what digital forensics is, the methodologies used, key technical concepts and the tools needed to perform examinations. Details on digital forensics for computers, networks, cell phones, GPS, the cloud, and Internet are discussed. Readers will also learn how to collect evidence, document the scene, and recover deleted data. This is the only resource your students need to get a jump-start into digital forensics investigations.

This book is organized into 11 chapters. After an introduction to the basics of digital forensics, the book proceeds with a discussion of key technical concepts. Succeeding chapters cover labs and tools; collecting evidence; Windows system artifacts; anti-forensics; Internet and email; network forensics; and mobile device forensics. The book concludes by outlining challenges and concerns associated with digital forensics. PowerPoint lecture slides are also available.

This book will be a valuable resource for entry-level digital forensics professionals as well as those in complimentary fields including law enforcement, legal, and general information security.

• Learn all about what Digital Forensics entails
• Build a toolkit and prepare an investigative plan
• Understand the common artifacts to look for during an exam

Chapter 1

Introduction

Information in This Chapter:

What Is Forensic Science?

What Is Digital Forensics?

Uses of Digital Forensics

Role of the Forensic Examiner in the Judicial System

American Society of Crime Laboratory Directors/Laboratory Accreditation Board, Electronic Discovery, Document and Media Exploitation (DOMEX), Scientific Working Group on Digital Evidence (SWGDE), American Academy of Forensic Sciences, CSI Effect

“Each betrayal begins with trust.”

—“Farmhouse” by the band Phish

Introduction

Your computer will betray you. This is a lesson that many CEO's, criminals, politicians, and ordinary citizens have learned the hard way. You are leaving a trail, albeit a digital one; it's a trail nonetheless. Like a coating of fresh snow, these 1s and 0s capture our “footprints” as we go about our daily life.

Cell phone records, ATM transactions, web searches, e-mails, and text messages are a few of the footprints we leave. As a society, our heavy use of technology means that we are literally drowning in electronically stored information. And the tide keeps rolling in. Don't believe me? Check out these numbers from the research company IDC:

The digital universe (all the digital information in the world) will reach 1.2 million petabytes in 2010. That's up by 62% from 2009.

If you can't get your head around a petabyte, maybe this will help:

“One petabyte is equal to: 20 million, four-drawer filing cabinets filled with text or 13.3 years of HD-TV video.”

(Mozy, 2009)

The impact of our growing digital dependence is being felt in many domains, not the least of which is the legal system. Everyday, digital evidence is finding its way into the world's courts. This is definitely not your father's litigation. Gone are the days when records were strictly paper. This new form of evidence presents some very significant challenges to our legal system. Digital evidence is considerably different from paper documents and can't be handled in the same way. Change, therefore, is inevitable. But the legal system doesn't turn on a dime. In fact, it's about as nimble as the Titanic. It's struggling now to catch-up with the blinding speed of technology.

Criminal, civil, and administrative proceedings often focus on digital evidence, which is foreign to many of the key players, including attorneys and judges. We all know folks who don't check their own e-mail or even know how to surf the Internet. Some lawyers, judges, businesspeople, and cops fit squarely into that category as well. Unfortunately for those people, this blissful ignorance is no longer an option.

Where law-abiding society goes, the bad guys will be very close behind (if not slightly ahead). They have joined us on our laptops, cell phones, iPads, and the Internet. Criminals will always follow the money and leverage any tools, including technology, that can aid in the commission of their crimes.

Although forensic science has been around for years, digital forensics is still in its infancy. It's still finding its place among the other more established forensic disciplines, such as DNA and toxicology. As a discipline, it is where DNA was many years ago. Standards and best practices are still being developed.

Digital forensics can't be done without getting under the hood and getting your hands dirty, so to speak. It all starts with the 1's and 0's. This binary language underpins not only the function of the computer but how it stores data as well. We need to understand how these 1's and 0's are converted into the text, images, and videos we routinely consume and produce on our computers.

What is Forensic Science?

Let's start by examining what it's not. It certainly isn't Humvees, sunglasses, and expensive suits. It isn't done without lots of paperwork, and it's never wrapped up in sixty minutes (with or without commercials). Now that we know what it isn't, let's examine what it is. Simply put, forensics is the application of science to solve a legal problem. In forensics, the law and science are forever integrated. Neither can be applied without paying homage to the other. The best scientific evidence in the world is worthless if it's inadmissible in a court of law.

What is Digital Forensics?

There are many ways to define digital forensics. In Forensic Magazine, Ken Zatyko defined digital forensics this way:

“The application of computer science and investigative procedures for a legal purpose involving the analysis of digital evidence after proper search authority, chain of custody, validation with mathematics, use of validated tools, repeatability, reporting, and possible expert presentation.”

(Zatyko, 2007)

Digital forensics encompasses much more than just laptop and desktop computers. Mobile devices, networks, and “cloud” systems are very much within the scope of the discipline. It also includes the analysis of images, videos, and audio (in both analog and digital format). The focus of this kind of analysis is generally authenticity, comparison, and enhancement.

Uses of Digital Forensics

Digital forensics can be used in a variety of settings, including criminal investigations, civil litigation, intelligence, and administrative matters.

Criminal Investigations

When you mention digital forensics in the context of a criminal investigation, people tend to think first in terms of child pornography and identity theft. Although those investigations certainly focus on digital evidence, they are by no means the only two. In today's digital world, electronic evidence can be found in almost any criminal investigation conducted. Homicide, sexual assault, robbery, and burglary are just a few of the many examples of “analog” crimes that can leave digital evidence.

One of the major struggles in law enforcement is to change the paradigm of the police and get them to think of and seek out digital evidence. Everyday digital devices such as cell phones and gaming consoles can hold a treasure trove of evidence. Unfortunately, none of that evidence will ever see a courtroom if it's not first recognized and collected. As time moves on and our law enforcement agencies are replenished with “younger blood,” this will become less and less of a problem.

Bind. Torture. Kill.

The case of Dennis Rader, better known as the BTK killer, is a great example of the critical role digital forensics can play in a criminal investigation. This case had national attention and, thanks to digital forensics, was solved thirty years later. To all that knew him before his arrest, Dennis Rader was a family man, church member, and dedicated public servant. What they didn't know was that he was also an accomplished serial killer. Dennis Rader, known as Bind, Torture, Kill (BTK), murdered ten people in Kansas from 1974 to 1991. Rader managed to avoid capture for over thirty years until technology betrayed him.

After years of silence, Rader sent a letter to the Wichita Eagle newspaper declaring that he was responsible for the 1986 killing of a young mother. The letter was received by the Eagle on March 19, 2004. After conferring with the FBI's Behavioral Analysis Unit, the police decided to attempt to communicate with BTK through the media.

In January 2005, Rader left a note for police, hidden in a cereal box, in the back of a pickup truck belonging to a Home Depot employee. In the note, he said:

“Can I communicate with Floppy and not be traced to a computer. Be honest. Under Miscellaneous Section, 494, (Rex, it will be OK), run it for a few days in case I'm out of town-etc. I will try a floppy for a test run some time in the near future-February or March.”

The police did the only thing they could. They lied. As directed, they responded (via an ad in the Eagle) on January 28. The ad read “Rex, it will be ok, Contact me PO Box 1st four ref.numbers at 67202.”

On February 16, a manila envelope arrived at KSAS, the Fox affiliate in Wichita. Inside was a purple floppy disc from BTK. The disc contained a file named “Test A.rtf.” (The .rtf extension stands for “Rich Text File”). A forensic exam of the file struck gold. The file's metadata (the data about the data) gave investigators the leads they had been waiting over thirty years for. Aside from the “Date Created” (Thursday, February 10, 2005 6:05:34 PM) and the “Date Modified” (Monday, February 14, 2005 2:47:44 PM) were the “Title” (Christ Lutheran Church) and “Last Saved By:” (Dennis).

Armed with this information, investigators quickly logged on to the Christ Lutheran Church web site. There they found that Dennis Rader was the president of the church's Congregation Council. The noose was tightening, but it wasn't tight enough. Investigators turned to DNA to make the case airtight. Detectives went on to obtain a DNA sample from Rader's daughter and compared it to DNA from BTK. The results proved that BTK was her father. On February 25, three days after the DNA sample arrived at the lab, Rader was arrested, sealing the fate of BTK. He is currently serving ten consecutive life sentences (Witchita Eagle).

Civil Litigation

The use of digital forensics in civil cases is big business. In 2011, the estimated total worth of the electronic discovery market is somewhere north of $780 million (Global EDD Group). As part of a proc...