A digital forensic process model provides a framework for conducting digital forensic investigations in a methodical manner. It outlines the key phases and steps involved in acquiring, analyzing, and reporting on digital evidence. Having a consistent process allows digital forensics to be conducted in a way that is legally defensible and ensures evidence integrity.
What are the main goals of a digital forensic process model?
The main goals of a digital forensic process model are:
- To provide a structured approach for investigating digital devices and data
- To maintain a chain of custody for digital evidence
- To ensure evidence integrity and admissibility in legal proceedings
- To guide examiners through the forensic process in a repeatable way
- To document procedures used during an examination for review
Following an accepted process model allows examiners to systematically collect and analyze digital evidence while minimizing disruption to the original data. This helps ensure the evidence can be relied upon in corporate investigations or criminal and civil litigation.
What are some commonly used digital forensic process models?
Some commonly used digital forensic process models include:
1. ABC model
The ABC model consists of three phases:
Acquisition – The suspect digital media is acquired using forensically sound processes to create a forensic copy for examination.
Analysis – The forensic copy is analyzed using a combination of automated tools and manual review to identify files and data of interest for the case.
Reporting – The examiner summarizes their findings in a report suitable for presentation in court.
2. NIST SP-800 model
Developed by the National Institute of Standards and Technology (NIST), this model defines the following four phases:
Collection – Identifying sources of potential digital evidence and acquiring it while preserving integrity.
Examination – Forensically processing collected data using a combination of automated and manual methods to assess its contents.
Analysis – Drawing conclusions based on the evidence found during examination and formulating theories about what happened.
Reporting – Reporting the outcomes of the analysis, which may be used in legal proceedings.
3. DFRWS model
The Digital Forensic Research Workshop (DFRWS) designed an investigative model with six phases:
Identification – Determining whether an incident has occurred and if digital forensics is needed.
Preparation – Developing tools, techniques, procedures, authorizations, and management support for the investigation.
Approach strategy – Determining the appropriate investigative methods to use, such as live forensics vs. post-mortem analysis.
Preservation – Ensuring the integrity and chain of custody for potential digital evidence.
Collection – Identifying digital sources, acquiring data, and verifying acquisition integrity.
Examination – Forensically processing collected evidence using a combination of automated and manual methods.
Analysis – Assessing results from the examination to draw conclusions about digital events.
Presentation – Summarizing findings in a report or presenting them for legal proceedings.
4. Integrated Digital Investigation Process (IDIP) model
The IDIP model defines the following 5 groups of activities:
Readiness Activities – Steps taken ahead of time to prepare tools, procedures, infrastructure, and authorizations to facilitate digital forensics when needed.
Deployment Activities – Deploying the preplanned tools, techniques, and procedures from readiness when an incident occurs.
Physical Crime Scene Investigation – Activities at the physical crime scene to identify and collect potential digital evidence sources.
Digital Crime Scene Investigation – Forensically acquiring data from seized devices and performing triage examination to identify areas for additional focus.
Review and Reporting Activities – Thorough examination of forensic copies, analysis of findings, report writing, and presentation for legal proceedings.
What are the key differences between common digital forensic models?
While models share some main phases in common, such as acquisition, examination, analysis, and reporting, some key differences include:
- Number of phases – Some models have 3 main phases while others have 6 or more granular steps.
- Specificity – Some models provide high-level guidance while others prescribe detailed procedures.
- Crime scene focus – Some models address physical crime scene investigation while others only cover digital steps.
- Pre-planning – Some models include upfront readiness while others start from incident response.
There is no one-size-fits-all model. Examiners may use aspects of multiple models based on case needs and jurisdictional requirements. However, using an accepted model helps reinforce digital forensics as a scientific process.
What are the core principles reflected in process models?
While process models vary, most reflect the following core principles:
- Evidence preservation – Following procedures to maintain chain of custody and evidence integrity.
- Documentation – Documenting each step taken to allow repeatability and review.
- Reproducible methodology – Applying a structured methodology consistently across cases.
- Legally defensible approach – Using court-tested tools and techniques.
- Unbiased collection and examination – Avoiding actions that could taint evidence or analysis.
- Comprehensive analysis – Pursuing all potential avenues of digital evidence.
- Verification and review – Validating findings and conclusions.
- Transparency – Communicating methodology and findings clearly.
Following an accepted process model helps instill these principles in a digital forensic investigation.
What are the typical phases of a digital forensics process model?
While models have distinct phases, at a high level, digital forensic investigations generally follow this sequence:
1. Initial response and preparation – Assessing the incident to determine if a digital forensic investigation is needed and laying the groundwork for evidence collection.
2. Evidence collection and acquisition – Systematically identifying sources of potential digital evidence, prioritizing them, and acquiring forensic copies.
3. Analysis and examination – Processing and manually reviewing forensic copies to uncover evidence related to the suspected incident.
4. Documentation and findings – Formally documenting the examination process and findings from the analysis.
5. Reporting and presentation – Summarizing conclusions and findings in a report format or for legal proceedings.
What steps are involved in the evidence acquisition phase?
The evidence acquisition phase typically involves:
- Inventorying devices and sources that may contain potential evidence
- Prioritizing evidence sources based on volatility, relevance, and other case factors
- Isolating devices from connectivity to preserve their state
- Documenting hardware and software parameters of the system
- Acquiring forensic duplications (“images”) of storage media using write-blocking and verification
- Transporting and storing forensic images securely while maintaining chain of custody
Proper acquisition by trained personnel is crucial to ensuring evidence integrity and admissibility.
What techniques are used in the examination and analysis phase?
The examination phase involves techniques such as:
- Identifying and decoding known and deleted files, partitions, and filesystem metadata
- Carving raw data to recover evidence that does not rely on filesystem structures
- Analyzing file signatures and headers to categorize file types found
- Filtering, sorting, and searching data using keywords, patterns, and other criteria
- Correlating evidence between multiple sources to uncover linkages and timelines
- Documenting observations from manual examination for triage and reporting
Tools automate parts of this process but human expertise is crucial to interpretation and contextual analysis.
How is the documentation and reporting phase conducted?
The documentation and reporting phase typically includes:
- Note taking throughout the investigation to track procedures, findings, and reasoning
- Summarizing case details, allegations, timelines, and key evidence uncovered
- Describing the tools, techniques, and process used during the examination
- Explaining how evidence supports conclusions and theories about the incident
- Inserting data excerpts, graphics, and charts to clarify technical evidence
- Applying the report to the original allegations and framing in context of the case
Thorough documentation allows reviewers and legal teams to understand the investigation and evidence without redoing it.
Why is following a digital forensic process model important?
Adhering to a structured digital forensics process model is crucial for several reasons:
- It maintains evidence integrity and chain of custody.
- It avoids errors or omissions through methodical procedures.
- It produces legally defensible evidence by design.
- It withstands judicial and defense scrutiny and challenges.
- It enables repeatability and peer review of findings.
- It reinforces digital forensics as a scientific discipline.
- It helps ensure examiner objectivity and neutrality.
- It saves time through planned triage of sources.
- It facilitates training, communication, and teamwork.
Documenting and following an accepted methodology is key to successful digital forensic investigations.
What can happen if proper process models are not followed?
Failing to adhere to a structured process model can jeopardize cases through:
- Evidence being ruled inadmissible in court due to gaps in chain of custody or improper handling.
- Investigative avenues being missed because steps were skipped or not documented.
- Mistakes, oversights, assumptions, or biases negatively impacting findings.
- Conclusions being discredited due to lack of repeatability or transparency.
- Findings being excluded because legally tested tools and methods were not used.
- Delays from lack of planning, coordination, or documentation.
- Higher costs from inefficiencies or unstructured efforts.
Lack of process exposes digital forensics to criticism as a pseudo-science and undermines its effectiveness for investigations. Adhering to a structured model mitigates these risks.
Conclusion
Digital forensic process models provide crucial frameworks for guiding the investigation of digital incidents in a methodical, transparent, and legally sound manner. While models may differ in their specifics, most outline phases for collection, examination, analysis, and reporting on digital evidence sources. Following an established process reinforces digital forensics as a scientific discipline and is vital for producing court-defensible findings. Documenting and implementing an appropriate model tailored to case needs is a hallmark of professional digital forensic practitioners.
