Disk Imaging
Creating a bit-for-bit copy of a storage device, including unallocated space, slack space and deleted-file remnants, so analysis is performed on the copy and never on the original. Formats include raw dd images and forensic containers such as E01 that embed metadata and checksums. Integrity is proven by hashing the source and the image and comparing, and the process is examined in GCFA, CHFI, GNFA and CySA+ forensics domains.
Why It Matters
In practice the distinction that matters is imaging versus copying: a file-level copy takes only allocated files and loses precisely what an investigation needs -- deleted content, slack space, filesystem metadata and unpartitioned regions. The integrity discipline is equally important, because an image whose hash was never recorded, or was recorded once and never verified, is difficult to defend when the analysis is challenged; standard practice hashes the source before imaging, hashes the resulting image, and records both with the tool and version used. Two situations complicate the textbook procedure: full-disk encryption means a powered-off image is useless without the key, so a live acquisition or key extraction from memory may be necessary, and modern SSDs with TRIM and wear levelling may have already destroyed deleted data that a spinning disk would have retained. On exams such as GCFA and CHFI, expect questions on why unallocated space matters and how integrity is demonstrated.
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Related Forensics terms
Digital Forensics
The scientific examination, collection, preservation, and analysis of digital evidence from computers, networks, mobile devices, and cloud environments for use in legal proceedings, incident response, or investigations. The forensic process follows strict procedures: identification, preservation (maintaining chain of custody), collection (creating forensic images), examination, analysis, and reporting. Key principles include working from forensic copies (never the original), documenting every action, and maintaining evidence integrity through cryptographic hashing. Tools include EnCase, FTK, Autopsy, and Volatility. Digital forensics is the focus of CHFI, GCFA, and GNFA certifications and is covered in CISSP Domain 7.
Chain of Custody
The documented and unbroken process of maintaining and controlling evidence to preserve its integrity and admissibility from the moment of collection through presentation in court. Every person who handles the evidence must be documented with dates, times, actions taken, and the reason for access. Any gap or irregularity in the chain of custody can cause evidence to be deemed inadmissible. In digital forensics, chain of custody includes hash verification at each transfer point, write-blocking during acquisition, and tamper-evident storage. This concept is critical for forensic examiners and is tested in CHFI, GCFA, and CISSP Domain 7 certifications.
Volatile Memory
Computer memory (RAM) that loses its contents when power is removed, making it a time-critical source of forensic evidence that must be captured before a system is shut down. Volatile memory contains running processes, open network connections, encryption keys, clipboard contents, logged-in users, and malware that may exist only in memory (fileless malware). Memory acquisition tools include FTK Imager, WinPmem, and LiME (Linux Memory Extractor), while analysis is performed with Volatility Framework or Rekall. The order of volatility (RFC 3227) dictates that RAM should be captured before disk, network, or other evidence. Memory forensics is a key skill in GCFA, CHFI, and incident response certifications.
Log Analysis
The examination of system, application, network, and security logs to identify security events, anomalies, policy violations, or evidence of attacks. Logs are generated by operating systems, firewalls, web servers, authentication systems, databases, and cloud services. Effective log analysis involves centralization (forwarding logs to a SIEM), normalization (standardizing formats), correlation (linking related events across sources), and alerting on suspicious patterns. Key log sources include Windows Event Logs, syslog, Apache/Nginx access logs, and cloud audit trails (AWS CloudTrail, Azure Activity Log). Log analysis is a core skill for SOC analysts and is tested in CySA+, CISSP, and GCIH certifications.
Memory Forensics
The forensic analysis of volatile memory (RAM) to extract evidence of malware, network connections, running processes, encryption keys, and other artifacts that may not be preserved on disk. Memory analysis can reveal malware that exists only in memory, decrypt encrypted volumes using keys in memory, and recover recently accessed data. Tools like Volatility, Rekall, and commercial memory analysis platforms enable automated analysis of memory dumps. Memory forensics is particularly valuable for analyzing advanced malware and rootkits that hide from traditional disk-based analysis.
Order of Volatility
The principle that digital evidence must be collected from most to least perishable, because acquiring one source can destroy another. The conventional order runs CPU registers and cache, then RAM, then network state and running processes, then temporary files, then disk, then remote logging and archival media. It governs live acquisition decisions in incident response and is examined in GCFA, GNFA, CHFI and CySA+ forensics domains.