Data Acquisition and Duplication

Module 4: Data Acquisition and Duplication

This module focuses on the methodologies, formats, and tools used to collect Electronically Stored Information (ESI) in a manner that is forensically sound and admissible in a court of law.

1. Fundamentals of Data Acquisition

  • Goal of Data Acquisition: To extract ESI from various media (computers, mobile devices, servers) to gain insight into a crime or incident.

  • Legally Defensible Process must be:

    • Auditable: Every step is logged.

    • Reproducible: Another investigator using the same tools should get the same results.

    • Integrity-Preserved: The data must be proven to be an exact copy of the original.

Core Rules of Acquisition

  1. Never Work on the Original Media: Work only on bit-stream copies to avoid accidental metadata changes.

  2. Use Clean Media: Destination drives must be sanitized (wiped) before use.

  3. Hash Everything: Use cryptographic hashes (e.g., MD5, SHA) to verify the copy matches the original 100%.

2. Live vs. Static Acquisition

Live Acquisition (System Powered ON)

  • Focus: Volatile Data—information stored in RAM that disappears when the power is cut.

  • Data Collected:

    • Running processes

    • Logged-on users

    • Network connections

    • Clipboard contents

    • Unencrypted data in memory

  • Risk: Running tools on a live system alters RAM. This is an "involuntary action" that must be documented.

Static/Dead Acquisition (System Powered OFF)

  • Focus: Non-Volatile Data stored on persistent media.

  • Data Collected:

    • Filesystem

    • Deleted files

    • Slack space

    • System logs

  • Requirement: Always use a Write Blocker to prevent the host OS from writing metadata (like "Last Accessed" dates) to the evidence drive.

3. Data Acquisition Formats

Format

Description

Pros/Cons

Raw (dd)

A bit-for-bit copy of the original media.

Pros: Universally compatible.
Cons: No metadata or compression; needs equal space.

Proprietary

Formats created by tools like FTK or EnCase (e.g., .E01).

Pros: Supports compression, splitting files, and embedding hashes.
Cons: May require specific software.

AFF/AFF4

Advanced Forensic Format (Open Source).

Pros: Fast, no size limits, supports metadata, highly organized.

4. The 8-Step Acquisition Methodology

Step 1: Determine Method

  • Decide between:

    • Logical Acquisition: specific files.

    • Sparse Acquisition: fragments/unallocated space.

    • Bit-stream Image: full drive.

  • In civil cases, smaller, targeted collections are often allowed.

Step 2: Select the Tool

  • The tool must be capable of creating a "qualified bit-stream copy."

  • Alerting: A critical feature is that the tool should warn you if the destination drive is smaller than the source (e.g., trying to copy 10TB to 5TB) to prevent mid-process corruption.

Step 3: Sanitize Target Media

  • Prior data on your destination drive can ruin an investigation.

  • Standards: Follow NIST, DoD, or GOST (Russian) standards for wiping.

  • Disposal: After the case, media must be destroyed/wiped to prevent unauthorized disclosure of Personally Identifiable Information (PII).

Step 4: Acquire Volatile Data

  • If the system is on, extract the RAM first.

  • Tool: Belkasoft Live RAM Capturer extracts memory into a .mem file.

  • PowerShell: Use the command Get-FileHash -Path [FilePath] -Algorithm MD5 | Format-List.

  • Warning: Loading the tool into RAM will alter the memory slightly; investigators must be aware of this impact.

Step 5: Enable Write Protection

  • Hardware: Use physical bridges (e.g., Tableau, CRU) to block "Write" commands at the hardware level.

  • Software: Use examiner-controlled OS settings or tools like SafeBlock if hardware isn't available.

Step 6: Acquire Non-Volatile Data

  • Once the system is off and write-blocked, image the hard drive.

  • Dead Acquisition: Remove the drive and connect it to a forensic workstation.

  • Tools: Use AccessData FTK Imager to create the image and verify it with an MD5/SHA hash.

Step 7: Planning for Contingencies

  • Expression: "Two is one, and one is none."

  • Multiple Copies: Always make at least two images to ensure redundancy. If one file becomes corrupt, the second is your backup.

  • Multiple Tools: It is best practice to create the first image with one tool (e.g., FTK Imager) and a second with another (e.g., ProDiscover) to validate the results.

  • Encryption: Be prepared for BitLocker (Windows). You must find the recovery key or the user-provided password to access the data.

Step 8: Validate the Acquisition

  • Perform a final hash comparison to ensure integrity.

  • Note: Raw format images do not contain internal metadata, so they require a separate manual validation process to ensure integrity.

Summary

  • Covered the importance of volatility, the differences between raw and proprietary formats, and the rigorous 8-step process required to ensure digital evidence stands up in court.

Next Step

  • In the next module, we explore Anti-Forensics—the tricks attackers use to hide their tracks.

Would you like me to create a quick-reference table of the common tools mentioned (Belkasoft, FTK Imager, etc.) and their specific uses?