Complete Digital Forensics Guide 2024: Investigation & Evidence Collection

Key Takeaways

Preserve evidence integrity—chain of custody is critical.
Never work on original evidence—use forensic copies.
Volatile evidence must be collected first (memory, network).

Document every action taken during investigation.
Use validated, write-blocking tools for acquisition.
Timeline analysis reconstructs events effectively.

1. Digital Forensics Overview
2. Evidence Collection
3. Disk Forensics
4. Memory Forensics

5. Network Forensics
6. Timeline Analysis
7. Forensics Tools
8. Frequently Asked Questions

1. Digital Forensics Overview

Digital forensics is the process of identifying, preserving, analyzing, and documenting digital evidence. It applies to criminal investigations, civil litigation, internal corporate investigations, and incident response. The goal is to reconstruct events, identify actors, and present findings that can withstand legal scrutiny.

Key principles include: evidence integrity, chain of custody, documentation, and reproducibility. Every action must be defensible in court.

Order of Volatility

Collect evidence in order of volatility (most volatile first):
1. CPU registers, cache
2. RAM (memory)
3. Network connections, running processes
4. Disk (file system)
5. Backup media, archives

2. Evidence Collection

2.1 Chain of Custody

# Chain of custody documentation:
- Who collected the evidence
- When it was collected
- Where it was collected from
- How it was secured
- Every transfer of custody
- Hash verification at each step

2.2 Collection Best Practices

Use write blockers for disk acquisition
Calculate and verify hash values (MD5, SHA256)
Photograph the scene before touching anything
Document everything in contemporaneous notes
Secure evidence in tamper-evident containers

3. Disk Forensics

3.1 Disk Acquisition

# Create forensic image using dd
dd if=/dev/sda of=/evidence/disk.img bs=4096 conv=sync,noerror

# Using dc3dd (with hashing)
dc3dd if=/dev/sda of=/evidence/disk.img hash=sha256 log=/evidence/log.txt

# FTK Imager (Windows GUI)
# Creates E01 (EnCase) format with metadata

3.2 File System Analysis

Recover deleted files from unallocated space
Analyze file metadata (timestamps, ownership)
Examine registry hives (Windows)
Extract browser history, cache, cookies
Review log files and event logs

Timestamps Can Be Manipulated

File system timestamps can be modified by attackers. Corroborate with other evidence: log files, network data, registry artifacts. Multiple independent sources increase confidence.

4. Memory Forensics

4.1 Memory Acquisition

# Linux memory dump
dd if=/dev/mem of=/evidence/memory.raw

# Windows using WinPMEM
winpmem.exe memory.raw

# FTK Imager, DumpIt (Windows GUI)

# Volatility 3 analysis
vol -f memory.raw windows.pslist
vol -f memory.raw windows.netscan
vol -f memory.raw windows.malfind

4.2 Memory Analysis Artifacts

Running processes and command lines
Network connections
Injected code and malware
Encryption keys
Credentials in memory
Clipboard contents

5. Network Forensics

5.1 Network Evidence Sources

Source	Evidence Type
PCAP captures	Full packet content
NetFlow/IPFIX	Connection metadata
Firewall logs	Allow/deny decisions
Proxy logs	URL access records
DNS logs	Domain lookups

5.2 Network Analysis

# Wireshark analysis
# Filter for C2 traffic, data exfiltration

# NetworkMiner (automated extraction)
# Extracts files, images, credentials from PCAP

# Zeek (network monitoring)
# Generates structured logs from traffic

6. Timeline Analysis

Timeline analysis correlates events from multiple sources (file system, logs, memory) into a single chronological view, revealing the sequence of attacker actions.

# Plaso/log2timeline
log2timeline.py timeline.plaso /evidence/disk.img
psort.py -o l2tcsv timeline.plaso -w timeline.csv

# Analyze in timeline explorer or spreadsheet

7. Forensics Tools

Tool	Purpose	Type
Autopsy	Disk forensics platform	Open Source
Volatility	Memory forensics	Open Source
FTK Imager	Disk imaging	Free
Wireshark	Network analysis	Open Source
EnCase	Full forensics suite	Commercial
X-Ways	Disk forensics	Commercial

SANS SIFT Workstation

SIFT is a free forensics distribution with pre-installed tools. It's maintained by SANS and used in their forensics courses. Great for learning and actual investigations.

8. Frequently Asked Questions

How do I get into digital forensics as a career?

Start with IT or security fundamentals. Learn forensics tools (Autopsy, Volatility). Get certifications (GCFE, EnCE). Practice on CTF challenges and public datasets. Many forensics roles require or prefer law enforcement or incident response background.

What if evidence is encrypted?

Encryption presents significant challenges. Options include: finding keys in memory, checking for recovery keys, examining password managers, or legal compulsion (court orders). Without keys, encrypted data may be unrecoverable.

Conclusion

Digital forensics requires methodical evidence collection, proper chain of custody, and thorough analysis across disk, memory, and network artifacts. Use validated tools, never work on original evidence, and document everything. Timeline analysis brings disparate evidence together to reconstruct events. Whether for incident response or legal proceedings, forensic rigor is essential.

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