Computer Forensics Principles and Practices

Computer ForensicsPrinciples and Practices by Volonino, Anzaldua, and Godwin Chapter 2: Computer Forensics and Digital Detective Work

Objectives • Recognize the role e-evidence plays in physical, or violent, and computer crimes • Describe the basic steps in a computer forensics investigation • Identify the legal and ethical issues affecting evidence search and seizure • Identify the types of challenges to the admissibility of e-evidence © Pearson Education Computer Forensics: Principles and Practices

Objectives (Cont.) • Understand how criminals’ motives can help in crime detection and investigation • Explain chain of custody • Explain why acceptable methods for computer forensics investigations and e-discovery are still emerging © Pearson Education Computer Forensics: Principles and Practices

Introduction Computer forensics investigators are “detectives of the digital world.” This chapter introduces you to the generally accepted methods used in computer forensics; computer architecture, the Internet, and digital devices, and the types of evidence these trails leave behind. © Pearson Education Computer Forensics: Principles and Practices

E-Evidence Trails and Hidden Files • Computers are routinely used to plan and coordinate many types of crimes • Computer activities leave e-evidence trails • File-wiping software can be used to delete data • File-wiping process takes time and expertise • Many e-evidence traces can be found by showing hidden files on a computer © Pearson Education Computer Forensics: Principles and Practices

Knowing What to Look For • Technical knowledge of how data and metadata are stored will determine what e-evidence is found • For this reason, technical knowledge of investigators must keep pace with evolving data storage devices © Pearson Education Computer Forensics: Principles and Practices

Knowing What to Look for (Cont.) • Three cases illustrate importance of technical knowledge: • Dr. Harold Shipman modified medical records to hide evidence of murder; date stamp revealed records were fraudulent • Employees made online purchases with customer credit cards; hidden HTML code revealed fraud • Neil Entwhistle killed his wife and child; cache showed Internet sites that described how to kill people © Pearson Education Computer Forensics: Principles and Practices

The Five Ws • Answering the 5 Ws helps in criminal investigations: • Who • What • Where • When • Why © Pearson Education Computer Forensics: Principles and Practices

In Practice: PDA Forensics • PDA forensics are being used frequently in homicide investigations and white collar crimes • Examples: • Danielle van Dam murder, February 2002 • Falsely billing for Medicaid and Medicare patients that were never seen © Pearson Education Computer Forensics: Principles and Practices

Preserving Evidence • Preserving evidence is critical in order to use the evidence in a legal defense or prosecution • Scientific methods must be used in order to preserve the integrity of the evidence collected © Pearson Education Computer Forensics: Principles and Practices

Computer Forensics Science • Consistent with other scientific research, a computer forensics investigation is a process • There are five stages to the process: • Intelligence • Hypothesis or Theory Formulation • Evidence Collection • Testing • Conclusion © Pearson Education Computer Forensics: Principles and Practices

Admissibility of Evidence • Goal of an investigation: collect evidence using accepted methods so that the evidence is accepted in the courtroom and admitted as evidence in the trial • Judge’s acceptance of evidence is called admission of evidence © Pearson Education Computer Forensics: Principles and Practices

Admissibility of Evidence (Cont.) • Evidence admissibility requires legal search and seizure and chain of custody • Chain of custody must include: • Where the evidence was stored • Who had access to the evidence • What was done to the evidence • In some cases, it may be more important to protect operations than obtain admissible evidence © Pearson Education Computer Forensics: Principles and Practices

In Practice: CD Universe Prosecution Failure • Attempted extortion involving credit card numbers by “Maxim” • Six months after the incident, Maxim still could not be found • Evidence was compromised by FBI and security firms who may have used original data rather than a forensic copy © Pearson Education Computer Forensics: Principles and Practices

Digital Signatures and Profiling • Digital signature left by serial killer • Dennis L. Rader revealed as “BTK” • Hidden electronic code on disk led to church where he had access to a computer • Digital profiling of crime suspects • E-evidence can supply patterns of behavior or imply motives • Evidence can include information stored on computers, e-mail, cell phone data, and wiretaps © Pearson Education Computer Forensics: Principles and Practices

Crimes Solved Using Forensics (Continued) © Pearson Education Computer Forensics: Principles and Practices

Crimes Solved Using Forensics(Cont.) © Pearson Education Computer Forensics: Principles and Practices

Protect the suspect system Discover all files Recover deleted files Reveal contents of hidden files Access protected or encrypted files Use steganalysis to identify hidden data Analyze data in unallocated and slack space Print an analysis of the system Provide an opinion of the system layout Provide expert testimony or consultation Forensics Investigation Methods • Methods used by investigators must achieve these objectives: © Pearson Education Computer Forensics: Principles and Practices

Unallocated Space and File Slack • Unallocated space: space that is not currently used to store an active file but may have stored a file previously • File slack: space that remains if a file does not take up an entire sector • Unallocated space and slack space can contain important information for an investigator © Pearson Education Computer Forensics: Principles and Practices

NYS Police Forensic Procedures (Continued) © Pearson Education Computer Forensics: Principles and Practices

NYS Police Forensic Procedures(Cont.) (Continued) © Pearson Education Computer Forensics: Principles and Practices

NYS Police Forensic Procedures(Cont.) © Pearson Education Computer Forensics: Principles and Practices

Challenges to Evidence • Criminal trials may be preceded by a suppression hearing • This hearing determines admissibility or suppression of evidence • Judge determines whether Fourth Amendment has been followed in search and seizure of evidence. • The success of any investigation depends on proper and ethical investigative procedures © Pearson Education Computer Forensics: Principles and Practices

Search Warrants • Investigators generally need a search warrant to search and seize evidence • Law officer must prepare an affidavit that describes the basis for probable cause—a reasonable belief that a person has committed a crime • Search warrant gives an officer only a limited right to violate a citizen’s privacy © Pearson Education Computer Forensics: Principles and Practices

Search Warrants(Cont.) • Two reasons a search can take place without a search warrant: • The officer may search for and remove any weapons that the arrested person may use to escape or resist arrest • The officer may seize evidence in order to prevent its destruction or concealment © Pearson Education Computer Forensics: Principles and Practices

In Practice: A Terrorist’s Trial • FBI agents attempted to get permission to search Moussaoui’s laptop but permission was denied on grounds they had not proved probable cause • Events on September 11 provided enough evidence for a search warrant, but by this time it was too late to access e-mail accounts that might have provided important data © Pearson Education Computer Forensics: Principles and Practices

Motives for Cybercrimes • Finding the motive—the “why” of the crime—can help in an investigation • Possible motives: • Financial gain, including extortion and blackmail • Cover up a crime • Remove incriminating information or correspondence • Steal goods or services without having to pay for them • Industrial espionage © Pearson Education Computer Forensics: Principles and Practices

Categories of Cybercrimes • Computer is the crime target • Computer is the crime instrument • Computer is incidental to traditional crimes • New crimes generated by the prevalence of computers © Pearson Education Computer Forensics: Principles and Practices

Chain of Custody Procedures • Handling of e-evidence must follow the three C’s of evidence: care, control, and chain of custody • Chain of custody procedures • Keep an evidence log that shows when evidence was received and seized, and where it is located • Record dates if items are released to anyone • Restrict access to evidence • Place original hard drive in an evidence locker • Perform all forensics on a mirror-image copy, never on the original data © Pearson Education Computer Forensics: Principles and Practices

Report Procedures • All reports of the investigation should be prepared with the understanding that they will be read by others • The investigator should never comment on the guilt or innocence of a suspect or suspects or their affiliations • Only the facts of the investigation should be presented; opinions should be avoided © Pearson Education Computer Forensics: Principles and Practices

Computer Forensics Investigator’s Responsibilities • Investigate and/or review current computer and computer-mediated crimes • Maintain objectivity when seizing and investigating computers, suspects, and support staff • Conduct all forensics investigations consistently with generally accepted procedures and federal rules of evidence and discovery • Keep a log of activities undertaken to stay current in the search, seizure, and processing of e-evidence © Pearson Education Computer Forensics: Principles and Practices

Summary • Computers and the Internet have contributed to traditional and computer crimes • Effective forensic investigation requires any technology that tracks what was done, who did it, and when • Images or exact copies of the digital media being investigated need to be examined by trained professionals © Pearson Education Computer Forensics: Principles and Practices

Summary (Cont.) • There are several legal and ethical issues of evidence seizure, handling, and investigation • New federal rules and laws regulate forensic investigations • The need for e-evidence has led to a new area of criminal investigation, namely computer forensics • This field is less than 15 years old © Pearson Education Computer Forensics: Principles and Practices

Summary (Cont.) • Computer forensics depends on an understanding of technical and legal issues • Greatest legal issue in computer forensics is the admissibility of evidence in criminal cases • Computer forensics investigators identify, gather, extract, protect, preserve, and document computer and other e-evidence using acceptable methods © Pearson Education Computer Forensics: Principles and Practices

Summary (Cont.) • Laws of search and seizure, as they relate to electronic equipment, must be followed • Failure to follow proper legal procedure will result in evidence being ruled inadmissible in court © Pearson Education Computer Forensics: Principles and Practices

Computer Forensics Principles and Practices