Performing File Carving with Foremost

When to Use

• When recovering files from unallocated disk space or corrupted file systems
• For extracting evidence from formatted or wiped storage media
• When file system metadata is unavailable but raw data sectors contain evidence
• During investigations requiring recovery of specific file types from raw images
• As a complement to file system-based recovery for maximum evidence extraction

Prerequisites

• Foremost installed on forensic workstation
• Forensic disk image in raw (dd) format
• Sufficient output storage (potentially larger than source)
• Custom foremost.conf for specialized file types (optional)
• Understanding of file signatures (magic bytes) for target file types
• Scalpel as an alternative for performance-critical carving

Workflow

Step 1: Install and Configure Foremost

# Install Foremost
sudo apt-get install foremost

# Verify installation
foremost -V

# Review default configuration
cat /etc/foremost.conf

# The default foremost.conf supports:
# jpg, gif, png, bmp - Image formats
# avi, exe, mpg, wav - Media and executables
# riff, wmv, mov, pdf - Documents and video
# ole (doc/xls/ppt), zip, rar - Office and archives
# htm, cpp, java - Text/code files

# Create custom configuration for additional file types
cp /etc/foremost.conf /cases/case-2024-001/custom_foremost.conf

# Add custom file signatures
cat << 'EOF' >> /cases/case-2024-001/custom_foremost.conf
# Custom additions for investigation
# Format: extension  case_sensitive  max_size  header  footer
    docx    y    10000000    \x50\x4b\x03\x04    \x50\x4b\x05\x06
    xlsx    y    10000000    \x50\x4b\x03\x04    \x50\x4b\x05\x06
    pptx    y    10000000    \x50\x4b\x03\x04    \x50\x4b\x05\x06
    sqlite  y    50000000    \x53\x51\x4c\x69\x74\x65\x20\x66\x6f\x72\x6d\x61\x74
    pst     y    500000000   \x21\x42\x44\x4e
    eml     y    1000000     \x46\x72\x6f\x6d\x3a    \x0d\x0a\x0d\x0a
    evtx    y    50000000    \x45\x6c\x66\x46\x69\x6c\x65
EOF

Step 2: Run Foremost Against the Disk Image

# Basic carving of all supported file types
foremost -t all \
   -i /cases/case-2024-001/images/evidence.dd \
   -o /cases/case-2024-001/carved/foremost_all/

# Carve only specific file types
foremost -t jpg,png,pdf,doc,xls,zip \
   -i /cases/case-2024-001/images/evidence.dd \
   -o /cases/case-2024-001/carved/foremost_targeted/

# Use custom configuration
foremost -c /cases/case-2024-001/custom_foremost.conf \
   -i /cases/case-2024-001/images/evidence.dd \
   -o /cases/case-2024-001/carved/foremost_custom/

# Carve from a specific partition offset
# First, find partitions
mmls /cases/case-2024-001/images/evidence.dd
# Then carve from unallocated space only
# Extract unallocated space with blkls
blkls -o 2048 /cases/case-2024-001/images/evidence.dd \
   > /cases/case-2024-001/unallocated.dd

foremost -t all \
   -i /cases/case-2024-001/unallocated.dd \
   -o /cases/case-2024-001/carved/foremost_unalloc/

# Verbose mode for detailed progress
foremost -v -t all \
   -i /cases/case-2024-001/images/evidence.dd \
   -o /cases/case-2024-001/carved/foremost_verbose/ 2>&1 | \
   tee /cases/case-2024-001/carved/foremost_log.txt

# Indirect mode (process standard input)
dd if=/cases/case-2024-001/images/evidence.dd bs=512 skip=2048 | \
   foremost -t jpg,pdf -o /cases/case-2024-001/carved/foremost_pipe/

Step 3: Use Scalpel for High-Performance Carving

# Install Scalpel (faster alternative based on Foremost)
sudo apt-get install scalpel

# Edit Scalpel configuration (uncomment desired file types)
cp /etc/scalpel/scalpel.conf /cases/case-2024-001/scalpel.conf
# Uncomment lines for target file types in the config

# Run Scalpel
scalpel -c /cases/case-2024-001/scalpel.conf \
   -o /cases/case-2024-001/carved/scalpel/ \
   /cases/case-2024-001/images/evidence.dd

# Scalpel with file size limits
# Edit scalpel.conf to set appropriate max sizes:
# jpg  y  5000000  \xff\xd8\xff  \xff\xd9
# pdf  y  20000000 %PDF  %%EOF

Step 4: Process and Validate Carved Files

# Review Foremost audit report
cat /cases/case-2024-001/carved/foremost_all/audit.txt

# The audit.txt contains:
# - Number of files found per type
# - Start and end offsets
# - File sizes

# Validate carved files
python3 << 'PYEOF'
import os
import subprocess
from collections import defaultdict

carved_dir = '/cases/case-2024-001/carved/foremost_all/'

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