MP3 Steganography
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Find hidden data in MP3 audio files using mp3stego, metadata analysis, and frame inspection.
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MP3 Steganography
MP3 files can hide data in ID3 tags, unused frame space, or deliberately introduced encoding quirks. They're a common vehicle for audio steganography in CTFs. Always check metadata first — the flag is often in a comment or custom ID3 tag.
Analysis Workflow
Step-by-Step Analysis
Metadata — check all ID3 fields
exiftool suspicious.mp3
# Look especially at: Comment, Title, Artist, Album, TXXX, PRIV, USLT
strings suspicious.mp3 | grep -iE "(flag|ctf|key|secret)"Check for embedded files
binwalk suspicious.mp3
binwalk -e suspicious.mp3
xxd suspicious.mp3 | tail -20 # data after MP3 frames?Try mp3stego decode
mp3stego -X suspicious.mp3 # without password
mp3stego -X -P "password" suspicious.mp3 # with known passwordOpen in Audacity — spectrogram view
- File → Import → Audio
- Dropdown on track → Spectrogram
- Check both channels for visual patterns (text, Morse code)
Tools
ID3 tags are at the start (ID3v2) or end (ID3v1) of MP3 files:
exiftool suspicious.mp3
id3info suspicious.mp3
id3v2 -l suspicious.mp3Key fields to check: COMM (comment), TXXX (user-defined text), USLT (lyrics), PRIV (private data), APIC (attached picture — extract and analyze it too).
Advanced Analysis
Checklist
-
exiftool→ check ALL ID3 tags (Comment, TXXX, PRIV, USLT, APIC) -
strings | grep flag→ direct string search -
binwalk -e→ embedded files -
mp3stego -X→ hidden data in MP3 encoding - Audacity → spectrogram view for visual patterns
- Check for data after last MP3 frame
- DeepSound (try with common passwords)
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