Analyzing Disk Image with Autopsy

What Is This

Analyzing Disk Image with Autopsy is a digital forensics skill focused on the examination and investigation of forensic disk images using the Autopsy platform. Autopsy is a widely used open-source digital forensics tool that provides a graphical user interface (GUI) for The Sleuth Kit (TSK), enabling investigators to efficiently analyze disk images in various formats such as raw (dd), E01 (EnCase), and AFF. This skill comprises methods for recovering deleted files, examining file system metadata, analyzing embedded artifacts, and building investigative timelines, all within a structured and repeatable workflow.

Why Use It

Forensic analysis of disk images is a cornerstone of incident response, malware investigations, data breach analysis, and digital evidence recovery. Autopsy bridges the gap between powerful command-line forensic tools and the need for accessible, comprehensive analysis. It enables both technical and non-technical users to:

• Recover files and artifacts that may have been deleted or hidden
• Analyze file system structures, timelines, and user activity
• Perform keyword searches and hash-based identification of known or suspicious files
• Generate visual reports suitable for technical teams, management, or legal proceedings
• Correlate evidence from multiple sources and build a complete case

Using Autopsy streamlines the forensic process, reduces the risk of manual errors, and offers a robust investigative platform that is extensible with modules for email, web, registry, and more.

How to Use It

Prerequisites

• Autopsy 4.x installed (Windows) or Autopsy 4.x with The Sleuth Kit (Linux)
• Forensic disk image (raw/dd, E01, or AFF format)
• Java Runtime Environment (JRE) 8 or higher
• At least 8GB RAM (16GB+ recommended for large images)
• Sufficient disk space for case database (2-3 times the image size)
• Optional: NSRL and known-bad hash databases for file identification

Step 1:

Install Autopsy and Set Up the Environment

On Linux

sudo apt-get update
sudo apt-get install sleuthkit autopsy

On Windows

Download the latest Autopsy 4.x installer from the official Autopsy website, and follow the installation instructions.

Step 2:

Launch Autopsy and Create a New Case

1. Open Autopsy.
2. Click "Create New Case".
3. Enter a case name, base directory, and optional case number or examiner details.
4. Click "Next" to proceed.

Step 3:

Add a Disk Image to the Case

1. Select "Add Data Source" - choose "Disk Image or VM File".
2. Browse to select your forensic image file (e.g., .E01, .dd, .img).
3. Specify the time zone for correct timestamp interpretation.
4. Click "Next" and let Autopsy process the image.

Step 4:

Configure Ingest Modules

Autopsy uses ingest modules to automatically analyze data as it is added. Recommended modules include:

• File Type Identification
• Hash Lookup (add NSRL or custom hash sets)
• Keyword Search (add custom keyword lists if needed)
• Recent Activity (browser history, downloads, etc.)
• Extract Registry Files (for Windows images)
• Email Parser (for mail file analysis)

Select the modules relevant to your investigation and click "Finish".

Step 5:

Analyze Results

Autopsy organizes findings in the left navigation pane under headings such as "Data Sources", "Views", and "Analysis Results". Key areas to investigate:

• File System: Browse all partitions, folders, and files - including deleted and system files.
• Keyword Hits: Review files and artifacts matching your keyword lists.
• Hash Set Hits: Identify known good or bad files based on hash set matches.
• Web Artifacts: Analyze browser history, cache, and downloads.
• User Activity: Investigate recent documents, USB device usage, and logins.
• Timeline: Visualize file creation, modification, and access events to reconstruct user actions.

Step 6:

Recover and Export Evidence

To recover deleted or suspicious files:

1. Right-click the file or artifact of interest.
2. Select "Extract File(s)" and specify an export location.

To generate reports:

1. Click "Generate Report" in the toolbar.
2. Select report type (HTML, Excel, CSV, etc.).
3. Choose which findings to include and finalize the report.

Code Example:

Command-Line File Recovery Using Sleuth Kit

For advanced users, The Sleuth Kit provides command-line flexibility. For example, to list all files in a disk image:

fls -r -m / image.dd

To recover a specific file by inode number:

icat image.dd <inode_number> > recovered_file.bin

These operations can complement GUI-based analysis in Autopsy.

When to Use It

• When a forensic disk image is available and requires structured, in-depth investigation
• During incident response or breach analysis where deleted or hidden files may contain evidence
• When visual reporting is required for stakeholders such as management or legal counsel
• For timeline reconstruction to understand the sequence of events on a system
• When correlating artifacts from multiple disk images as part of a broader case

Important Notes

• Always work with forensic copies - never analyze original evidence directly to preserve integrity.
• Ensure your analysis environment is isolated from production networks to avoid contamination.
• Large disk images can require substantial memory and disk space - monitor system resources during analysis.
• The accuracy of hash lookup depends on the quality and scope of your hash databases.
• Document all actions in your investigation for chain of custody and repeatability.
• Autopsy’s modular design allows for integration with third-party plugins, extending its capabilities for specialized analysis.
• Keep Autopsy and all forensic tools updated to avoid compatibility and security issues.

By mastering disk image analysis with Autopsy, investigators can efficiently uncover, document, and report digital evidence in a methodical, defensible manner.