mukul975 Performing Disk Forensics Investigation
When to Use
- A security incident requires forensic analysis of a system's persistent storage
- Evidence preservation is needed for potential legal proceedings or HR investigations
- Deleted files, browser history, or application artifacts must be recovered
- A timeline of user or adversary activity must be reconstructed from file system metadata
- Malware persistence mechanisms stored on disk need identification and documentation
Do not use for volatile evidence (running processes, network connections); use memory forensics with Volatility instead.
Prerequisites
- Forensic workstation with write-blocking hardware or software (Tableau T35u, Arsenal Image Mounter)
- Forensic imaging software: FTK Imager, Guymager, or dd with dcfldd
- Analysis platform: Autopsy, FTK (Forensic Toolkit), or X-Ways Forensics
- Sufficient storage (2-3x the target drive size for image plus working copies)
- Chain of custody forms and evidence bags for physical media
- Hash verification tools for evidence integrity (SHA-256)
Workflow
Step 1: Secure and Document the Evidence
Before touching any storage media, establish chain of custody:
- Photograph the system, noting serial numbers, labels, and cable connections
- Document the evidence source: device type, make, model, serial number, capacity
- Complete chain of custody form with date, time, handler name, and reason for acquisition
- Use a hardware write blocker when connecting the evidence drive to the forensic workstation
Chain of Custody Record:
━━━━━━━━━━━━━━━━━━━━━━━
Case ID: INC-2025-1547
Evidence ID: EVD-001
Description: Samsung 870 EVO 500GB SSD
Serial Number: S5XXNJ0R912345
Source Host: WKSTN-042
Acquired By: [Analyst Name]
Date/Time: 2025-11-15T16:30:00Z
Write Blocker: Tableau T35u (S/N: T35U-12345)
Step 2: Create a Forensic Image
Produce a bit-for-bit copy of the evidence drive:
Using FTK Imager (Windows):
- Connect evidence drive through write blocker
- File > Create Disk Image > Select source drive
- Choose E01 (Expert Witness Format) for compression and metadata
- Set destination path and evidence item information
- Enable "Verify images after they are created"
- Record source and image hash values
Using dcfldd (Linux):
# Create raw image with hash verification
dcfldd if=/dev/sdb of=/evidence/WKSTN-042.dd \
hash=sha256 hashlog=/evidence/WKSTN-042.sha256 \
bs=4096 conv=noerror,sync
# Verify image integrity
sha256sum /evidence/WKSTN-042.dd
Imaging Summary:
Source Drive: /dev/sdb (Samsung 870 EVO 500GB)
Image File: WKSTN-042.E01
Image Format: E01 (Expert Witness)
Source Hash: SHA-256: a1b2c3d4e5f6...
Image Hash: SHA-256: a1b2c3d4e5f6... (MATCH)
Sectors Read: 976,773,168
Errors: 0
Duration: 47 minutes
Step 3: Analyze File System Structure
Open the forensic image in Autopsy or FTK and examine the file system:
- Identify partition layout (MBR/GPT, NTFS/ext4/APFS partitions)
- Examine the Master File Table (MFT) for NTFS or inode tables for ext4
- Identify deleted files and directories (marked as unallocated but not yet overwritten)
- Recover files from unallocated space using file carving
- Examine alternate data streams (NTFS ADS) for hidden data
Key Windows Artifacts to Examine:
User Activity:
- NTUSER.DAT (registry hive per user)
- UsrClass.dat (shellbags, file access history)
- Recent files: %AppData%\Microsoft\Windows\Recent\
- Jump lists: %AppData%\Microsoft\Windows\Recent\AutomaticDestinations\
Program Execution:
- Prefetch: C:\Windows\Prefetch\*.pf
- Amcache: C:\Windows\appcompat\Programs\Amcache.hve
- SRUM: C:\Windows\System32\SRU\SRUDB.dat
- ShimCache: SYSTEM registry hive
Persistence:
- Scheduled Tasks: C:\Windows\System32\Tasks\
- Startup folders: %AppData%\Microsoft\Windows\Start Menu\Programs\Startup\
- Services: SYSTEM registry hive
Network:
- WLAN profiles: C:\ProgramData\Microsoft\Wlansvc\Profiles\
- Browser history: Chrome, Firefox, Edge profile directories
Step 4: Reconstruct the Timeline
Build a comprehensive timeline of file system activity:
Using Autopsy Timeline Module:
- Generate timeline from all available sources (MFT, event logs, browser history, prefetch)
- Filter to the investigation timeframe
- Identify clusters of activity correlating with the incident
- Document the sequence of attacker actions based on file creation, modification, and access timestamps
Using The Sleuth Kit (command line):
# Generate body file from NTFS image
fls -r -m / WKSTN-042.dd > bodyfile.txt
# Create timeline from body file
mactime -b bodyfile.txt -d > timeline.csv
# Filter timeline to investigation period
grep "2025-11-15" timeline.csv | sort > incident_timeline.csv
Step 5: Recover and Analyze Artifacts
Extract and analyze specific forensic artifacts:
- Prefetch files: Parse with PECmd to determine program execution times and loaded DLLs
- Event logs: Parse with EvtxECmd for Windows XML Event Logs
- Registry: Parse with RegRipper or Registry Explorer for user activity and system configuration
- Browser artifacts: Parse with Hindsight (Chrome), KAPE, or DB Browser for SQLite databases
- USB device history: Extract from SYSTEM\CurrentControlSet\Enum\USBSTOR registry key
- $MFT analysis: Parse with MFTECmd for detailed file metadata including $SI and $FN timestamps
Step 6: Document Findings
Compile a forensic analysis report suitable for legal proceedings:
- Maintain evidence integrity documentation (hash chain)
- Document every tool used and its version
- Record all analysis steps in a reproducible manner
- Present findings factually without conjecture
- Clearly distinguish between facts (observed data) and interpretations (analyst conclusions)
Key Concepts
| Term | Definition |
|---|---|
| Forensic Image | Bit-for-bit copy of storage media that preserves all data including deleted files and unallocated space |
| Write Blocker | Hardware or software device that prevents any modification to evidence media during acquisition |
| E01 Format | Expert Witness Format used by EnCase and FTK; supports compression, metadata, and built-in hash verification |
| File Carving | Recovery technique that searches unallocated disk space for file headers and footers to reconstruct deleted files |
| MFT (Master File Table) | NTFS metadata structure containing entries for every file and directory, including deleted entries |
| MAC Timestamps | Modified, Accessed, Created timestamps on files used for timeline reconstruction (NTFS also has Entry Modified) |
| Prefetch | Windows artifact recording program execution metadata; contains execution count, timestamps, and loaded DLLs |
| Unallocated Space | Disk sectors not assigned to any file; may contain remnants of deleted files recoverable through carving |
Tools & Systems
- FTK Imager: Free forensic imaging tool supporting E01, AFF, and raw formats with built-in hash verification
- Autopsy: Open-source digital forensics platform built on The Sleuth Kit for comprehensive disk analysis
- KAPE (Kroll Artifact Parser and Extractor): Triage collection and parsing tool for rapid artifact extraction
- X-Ways Forensics: Commercial forensic analysis tool known for speed and efficiency on large datasets
- Eric Zimmerman's Tools: Suite of free forensic parsers (PECmd, MFTECmd, EvtxECmd, RegRipper) for Windows artifacts
Common Scenarios
Scenario: Employee Data Theft Investigation
Context: An employee submitted a resignation and is suspected of copying proprietary files to a USB drive before departing. HR requests a forensic investigation of the employee's workstation.
Approach:
- Image the workstation disk using FTK Imager with a write blocker
- Parse USB device history from SYSTEM registry to identify connected devices
- Examine ShellBags and Jump Lists for evidence of file browsing and copying to removable media
- Parse LNK files in the Recent folder to identify recently accessed documents
- Analyze browser history for personal cloud storage uploads (Google Drive, Dropbox)
- Build a timeline correlating USB connections with file access events
Pitfalls:
- Failing to image the drive before the IT department reassigns the workstation
- Not checking cloud storage browser history alongside USB evidence
- Overlooking Volume Shadow Copies that may contain earlier versions of deleted files
- Presenting analysis conclusions as fact without supporting evidence documentation
Output Format
DISK FORENSICS INVESTIGATION REPORT
=====================================
Case ID: INC-2025-1547
Evidence: EVD-001 (Samsung 870 EVO 500GB SSD)
Examiner: [Name]
Date of Analysis: 2025-11-16
EVIDENCE INTEGRITY
Source Hash: SHA-256: a1b2c3d4e5f6...
Image Hash: SHA-256: a1b2c3d4e5f6... (VERIFIED MATCH)
Write Blocker: Tableau T35u
PARTITION LAYOUT
Partition 1: NTFS 100 MB (System Reserved)
Partition 2: NTFS 465 GB (C: - OS and Data)
Partition 3: NTFS 500 MB (Recovery)
KEY FINDINGS
1. [Timestamp] - Malware dropper created in %TEMP% (update.exe)
2. [Timestamp] - Scheduled task "WindowsUpdate" created for persistence
3. [Timestamp] - Prefetch shows 14 executions of update.exe
4. [Timestamp] - USB device "Kingston DataTraveler" connected
5. [Timestamp] - 847 files copied to E:\ drive (ShellBag evidence)
RECOVERED ARTIFACTS
- 3 deleted malware samples recovered from unallocated space
- Browser history showing C2 panel access
- Registry evidence of disabled security software
TIMELINE
[Chronological event listing with timestamps and evidence sources]
TOOLS USED
- FTK Imager 4.7.1 (imaging)
- Autopsy 4.21.0 (analysis)
- PECmd 1.5.0 (prefetch parsing)
- MFTECmd 1.2.2 (MFT analysis)