Digital Forensics Master Guide: Disk Imaging, Hashing, Evidence Integrity & DFIR Investigation (Beginner to Architect Level)
Digital Forensics and Incident Response (DFIR) is the scientific process of collecting, preserving, analyzing, and presenting digital evidence. This complete master guide takes you step-by-step from beginner concepts to advanced forensic architecture used by professional investigators, SOC analysts, and cybersecurity experts.
1. Beginner Level — Introduction to Digital Forensics
Digital forensics focuses on investigating digital devices after security incidents, cybercrime, or legal disputes. The primary goal is to preserve evidence without altering it.
Main Objectives
- Maintain evidence integrity.
- Recover deleted or hidden data.
- Identify attacker behavior.
- Produce legally admissible findings.
2. Beginner — What is Disk Imaging?
Disk imaging is the process of creating an exact bit-by-bit copy of a storage device. Unlike normal copying, forensic imaging captures all sectors including deleted data.
- Active files
- Deleted files
- Unallocated space
- Slack space
- Filesystem metadata
Basic Workflow
Source Disk → Write Blocker → Forensic Workstation → Image File
3. Intermediate Level — Diagram Explanation
Source Drive (Evidence)
The original storage device containing data under investigation. Investigators must avoid modifying it.
Hardware Write Blocker
A write blocker ensures read-only access.
IF command == WRITE BLOCK ELSE ALLOW READ
Forensic Workstation
Specialized software performs sector-by-sector imaging.
Destination Drive
Stores the forensic image for analysis.
4. Intermediate — SHA-256 Hashing Explained
Hashing verifies data integrity by generating a unique digital fingerprint.
How SHA-256 Works
- Data padded into 512-bit blocks.
- 64 compression rounds.
- Bitwise logical operations.
T1 = h + Σ1(e) + Ch(e,f,g) + K[t] + W[t] T2 = Σ0(a) + Maj(a,b,c)
Matching hashes confirm the forensic image is identical to original evidence.
5. Advanced Level — Hex-Level Disk Structure
At a low level, disks contain binary sectors.
| Boot Sector | Metadata | File Data | Slack Space | Unallocated |
Forensic tools analyze hex data to detect hidden artifacts.
6. Advanced — Deleted File Recovery
Deleting files usually removes only filesystem references. The data remains until overwritten.
Recovery Process
- Analyze filesystem tables.
- Scan unallocated sectors.
- Carve files using signatures.
Example file signatures:
- JPEG = FF D8 FF
- PDF = 25 50 44 46
7. Advanced — Timeline Analysis (MFT & Journal)
NTFS Master File Table (MFT)
- Creation timestamp
- Modification timestamp
- Access timestamp
- Metadata change timestamp
USN Journal
Tracks filesystem changes and helps reconstruct attacker timelines.
8. Expert Level — Memory vs Disk Forensics
| Disk Forensics | Memory Forensics |
|---|---|
| Historical data | Live processes |
| Deleted files | Encryption keys |
| Filesystem artifacts | Injected malware detection |
9. Expert — Anti-Forensics Techniques
- Timestomping
- Log wiping
- Secure deletion
- Memory-only malware
Investigators detect manipulation by correlating multiple artifacts.
10. Architect Level — Enterprise DFIR Workflow
Detection → Isolation → Imaging → Hash Verification → Analysis → Timeline Reconstruction → Reporting
- Never analyze original evidence.
- Always verify hashes.
- Maintain chain of custody.
- Use layered forensic analysis.
Conclusion
Digital forensics combines low-level disk analysis, cryptographic validation, and investigative methodology. Understanding the progression from basic imaging to advanced forensic architecture enables cybersecurity professionals to conduct reliable and legally defensible investigations.
