The Basics of Digital Forensics
The Primer for Getting Started in Digital Forensics
By John Sammons
Elsevier Science Copyright © 2012 Elsevier, Inc.
All rights reserved.
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
Each betrayal begins with trust." —"Farmhouse" by the band Phish
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."
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."
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.
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).
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 process known as Electronic Discovery (eDiscovery), digital forensics has become a major component of much high dollar litigation. eDiscovery "refers to any process in which electronic data is sought, located, secured, and searched with the intent of using it as evidence in a civil or criminal legal case" (TechTarget, 2005).
In a civil case, both parties are generally entitled to examine the evidence that will be used against them prior to trial. This legal process is known as "discovery." Previously, discovery was largely a paper-based exercise, with each party exchanging reports, letters, and memos; however, the introduction of digital forensics and eDiscovery has greatly changed this practice.
The proliferation of the computer has rendered that practice nearly extinct. Today, parties no longer talk about filing cabinets, ledgers, and memos; they talk about hard drives, spreadsheets, and file types. Some paper-based materials may come into play, but it's more the exception than the rule. Seeing the evidentiary landscape rapidly changing, the courts have begun to modify the rules of evidence. The rules of evidence, be they state or federal rules, govern how digital evidence can be admitted during civil litigation. The Federal Rules of Civil Procedure were changed in December 2006 to specifically address how electronically stored information is to be handled in these cases.
Digital evidence can quickly become the focal point of a case, no matter what kind of legal proceeding it's used in. The legal system and all its players are struggling to deal with this new reality.
Terrorists and foreign governments, the purview of our intelligence agencies, have also joined the digital age. Terrorists have been using information technology to communicate, recruit, and plan attacks. In Iraq and Afghanistan, our armed forces are exploiting intelligence collected from digital devices brought straight from the battlefield. This process is known as DOMEX (Document and Media Exploitation). DOMEX is paying large dividends, providing actionable intelligence to support the soldiers on the ground (U.S. Army).
It's well documented that the 9-11 hijackers sought out and received flight training in order to facilitate the deadliest terrorist attack ever on U.S. soil. Digital forensics played a role in the investigation of this aspect of the attack.
On August 16, 2001, Zacarias Moussaoui was arrested by INS agents in Eagan, Minnesota, for overstaying his visa. Agents also seized a laptop and floppy disk. After obtaining a search warrant, the FBI searched these two items on September 11, 2001. During the analysis, they found evidence of a Hotmail account (firstname.lastname@example.org) used by Moussaoui. He used this account to send e-mail to the flight school as well as other aviation organizations.
For those not familiar with Hotmail accounts, it's a free e-mail service offered by Microsoft, similar to Gmail and Yahoo!. They're quite easy to get and only require basic subscriber information. This information is essentially meaningless, because none of the information is verified. During the examof Moussaoui's e-mail, agents were also able to analyze the Internet protocol connection logs. One of the IP addresses identified was assigned to "PC11" in a computer lab at the University of Oklahoma.
The investigation further showed that Moussaoui and the rest of the nineteen hijackers made extensive use of computers at a variety of Kinko's store locations in other cities. Agents arrived at the Kinko's in Eagan hoping to uncover evidence. They were disappointed to learn that this specific Kinko's makes a practice of erasing the drives on their rental computers every day. Now forty-four days after Moussaoui's visit, the agents felt the odds of recovering any evidence would be somewhere between slim and none. They didn't bother examining the Kinko's computer. The Eagan store isn't alone. Other locations make a routine practice of erasing or reimaging the rental computers as well. This is done periodically, some as soon as twenty-four hours, others as long as thirty days. The drives are erased to improve the performance and reliability of the computers as well as to protect the privacy of its customers (Lawler, 2002).
Excerpted from The Basics of Digital Forensics by John Sammons. Copyright © 2012 by Elsevier, Inc.. Excerpted by permission of Elsevier Science.
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