Certified: The CISSP Prepcast

Welcome to The Bare Metal Cyber CISSP Prepcast. This series helps you prepare for the ISC squared CISSP exam with focused explanations and practical context.
In this episode, we’re diving into the crucial world of Evidence Acquisition and Preservation. These practices are at the heart of digital forensics, enabling organizations to conduct reliable investigations, maintain compliance with legal and regulatory frameworks, and ensure that any digital evidence collected can withstand scrutiny in court. If you’ve followed the last few episodes, you know that digital forensics is not just about technical expertise—it’s about process integrity, evidence reliability, and organizational accountability. Proper acquisition and preservation are what transform raw data into defensible evidence, capable of supporting legal actions and guiding post-incident decisions.
Let’s begin by understanding what evidence acquisition really means. In the context of cybersecurity investigations, evidence acquisition refers to the structured and methodical collection of digital data from various sources. These sources may include hard drives, removable media, mobile devices, network traffic captures, server logs, system memory, or cloud service containers.
The purpose of acquisition is to capture exactly what exists at a given point in time—nothing more, nothing less. This requires care. You are not just copying files; you are capturing entire digital environments, including metadata, timestamps, and hidden files. The goal is to create a snapshot that preserves the integrity and usability of the data for future analysis and legal review.
When acquisition is done properly, it guarantees that the evidence has not been altered, tampered with, or corrupted during the process. This is essential for maintaining the chain of custody and ensuring that your findings hold up under legal scrutiny. Without proper acquisition, even the most compelling evidence could be dismissed in a court of law.
Effective acquisition techniques help minimize the risk of data contamination or loss. They ensure that the collected evidence is complete and that it accurately represents the digital state of the system at the time of the incident. A well-documented acquisition process also supports internal accountability and demonstrates that your organization is applying recognized forensic standards.
Let’s now focus on what makes evidence acquisition effective. The process begins with a comprehensive plan. Before any data is collected, forensic teams should define their objectives, identify target systems, select appropriate tools, and determine exactly what data needs to be captured. Plans should account for access permissions, system availability, and the urgency of the investigation.
Forensic tools used during acquisition must be validated. This means that they have been tested and proven to perform reliably without altering the source data. Common tools include forensic disk imagers, memory capture tools, and network traffic analyzers. Using untested or inappropriate tools risks damaging the evidence or introducing inaccuracies.
Forensic professionals must capture complete, unaltered images of digital evidence—typically using bit-by-bit disk imaging. These images are accompanied by cryptographic hashes, which are like digital fingerprints. The hash value is generated before and after acquisition to verify that the image is identical to the original. If the hash values match, the data has not been altered.
Throughout the acquisition, detailed documentation is essential. Teams should record timestamps, collection methods, tool versions, and the names of all personnel involved. This documentation forms part of the audit trail and supports future validation of the process.
Timing matters. Evidence should be collected as soon as possible after an incident to minimize the chances of tampering, deletion, or system changes. Delays in acquisition can result in volatile data being lost or overwritten. Quick action, supported by pre-defined procedures, ensures the reliability of the data and the success of the investigation.
Now let’s talk about why preservation is just as important as acquisition. Once evidence is collected, it must be stored and maintained in a secure manner. Evidence preservation ensures that the acquired data remains intact, unaltered, and accessible throughout the duration of the investigation and any associated legal proceedings.
Preservation practices are designed to prevent evidence degradation, corruption, or loss. These risks are real, particularly when dealing with fragile or volatile digital environments. For instance, storage media can degrade, files can become corrupted, or backups may fail. Preservation is about guarding against these risks through structured, documented, and secure procedures.
Preservation also guards against unauthorized access. If a sensitive piece of evidence is accidentally accessed or modified—even by well-meaning personnel—it may be considered compromised. That’s why secure storage environments with robust access controls are so critical.
Clear documentation is once again essential. Preservation records should show how evidence was stored, who accessed it, when it was moved, and under what conditions. These records establish a verifiable chain of custody and prove that the evidence has remained under controlled conditions.
Effective preservation practices support defensible investigations. They satisfy legal and regulatory expectations and ensure that your organization can respond confidently to questions from auditors, attorneys, or executives. Preserved evidence also supports future incident reviews and lessons-learned exercises, making it a valuable resource even after an investigation concludes.
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Now let’s discuss how to implement proper preservation procedures. First, establish a secure evidence storage environment. This means using physical and digital safeguards, including locked cabinets, tamper-evident packaging, secure servers, encryption, and climate-controlled facilities.
Chain-of-custody documentation should be integrated into every preservation process. A standardized form should accompany every piece of evidence, recording each transfer, the individual responsible, and the conditions under which it was stored. These forms should be kept secure and updated immediately whenever an action is taken.
Encryption plays a major role in protecting stored digital evidence. Data should be encrypted both at rest and during transit. Access controls should limit who can view or manipulate the evidence, and all access should be logged.
Preservation is not a one-time event. Regular audits and inspections are necessary to verify the integrity of stored evidence. This includes checking hash values, verifying backup systems, and confirming that storage conditions still meet forensic standards.
Finally, provide thorough training for all personnel who may be involved in preservation. They must understand both the technical aspects and the legal importance of protecting evidence. This training should be ongoing and include practice drills and updates based on new technologies or policy changes.
Let’s now look at the broader security controls that support both acquisition and preservation. Validated forensic tools are essential. These tools must be recognized, regularly tested, and consistently applied. Use only trusted sources and ensure that analysts are trained in their proper use.
Logging and access controls help maintain secure repositories. These systems must monitor who accesses forensic data and when. Real-time monitoring and anomaly detection can help identify unauthorized actions or potential evidence tampering.
Secure communication channels are also necessary—especially when transferring forensic data between locations or sharing it with law enforcement, legal counsel, or regulators. Encrypted email, virtual private networks, and secure file transfer protocols should all be used to reduce the risk of interception.
Audit your evidence management practices regularly. Look for gaps in procedure, weaknesses in storage infrastructure, or inconsistencies in documentation. Vulnerability assessments and penetration testing can help you uncover and correct issues before they undermine your investigations.
Lastly, maintain secure and redundant archival systems. Forensic evidence may need to be retained for years, especially in regulatory cases or civil litigation. Your archives must be secure, well-documented, and resilient to disaster.
Let’s close with continuous improvement. Evidence acquisition and preservation practices should evolve as threats change, legal requirements shift, and technologies advance. Regularly review your processes, update your tools, and revise your policies.
Use lessons learned from actual incidents. What went well during the last forensic investigation? What caused delays or confusion? Use that feedback to refine your approach and close gaps.
Foster cross-functional collaboration. Work with legal, compliance, IT, and executive leadership to ensure that everyone understands their role in managing digital evidence.
Keep training current. Ensure all staff involved in forensic work are certified, well-practiced, and updated on emerging threats and techniques. Invest in scenario-based exercises that simulate real-world investigations.
Thank you for tuning into the CISSP Prepcast by Bare Metal Cyber. Visit baremetalcyber.com for additional episodes, comprehensive CISSP study resources, and personalized certification support. Strengthen your understanding of Evidence Acquisition and Preservation, and we'll consistently support your journey toward CISSP certification success.