Steganography
Index of all steganography pages - image, audio, file, and text-based data hiding techniques.
Steganography
Steganography is the art of hiding data in plain sight. Unlike encryption, which makes data unreadable, steganography hides data inside innocent-looking files — images, audio, text — so that no one suspects there's a secret at all. In CTFs, stego challenges give you a file and ask you to find the flag hidden somewhere inside it.
The key difference from forensics: forensics examines what happened (logs, memory, network traffic), while steganography asks "what's hidden inside this file that looks normal?"
Pages in This Section
Image Steganography
| Page | Difficulty | What You'll Learn |
|---|---|---|
| LSB Steganography | Beginner | Extract data hidden in the least significant bits of pixels |
| PNG Analysis | Intermediate | PNG chunk structure, data after IEND, dimension tricks |
| JPEG Analysis | Beginner | steghide, data after EOF, EXIF metadata hiding |
| Pixel Manipulation | Intermediate | Channel XOR, alpha hiding, palette tricks, image diff |
Audio Steganography
| Page | Difficulty | What You'll Learn |
|---|---|---|
| Spectrograms | Beginner | Visual data hidden in frequency-time plots |
| MP3 Steganography | Beginner | mp3stego, ID3 tags, DeepSound, frame analysis |
File Steganography
| Page | Difficulty | What You'll Learn |
|---|---|---|
| File Magic Bytes | Beginner | Identify corrupted headers, fix magic bytes, detect polyglots |
| Polyglot Files | Intermediate | Files valid in two formats simultaneously (PNG+ZIP, etc.) |
Text Steganography
| Page | Difficulty | What You'll Learn |
|---|---|---|
| Whitespace Steganography | Beginner | SNOW, tab/space encoding, zero-width characters |
| Unicode Steganography | Intermediate | Homoglyphs, variation selectors, invisible Unicode |
The Universal First Step
Before running any specialized steg tool, do this on every challenge file:
file suspicious_file # what is it really?
exiftool suspicious_file # metadata (Comment field hides flags)
strings suspicious_file | grep -iE "(flag|ctf|key|secret)" # quick win
binwalk suspicious_file # embedded files?This takes 10 seconds and solves a surprising number of stego challenges. The flag is often in a metadata comment, an embedded archive, or as plaintext in the binary.
Aperisolve (aperisolve.com) is the fastest starting point for any image challenge — upload the image and it runs zsteg, strings, binwalk, exiftool, and bit plane analysis automatically.
Detection Workflow
Learning Path
Beginner — Start Here
- File Magic Bytes — Every file has magic bytes. Learn to identify, fix, and exploit them.
- JPEG Analysis — steghide, EXIF metadata, data after EOF. The most common stego challenge type.
- LSB Steganography — The foundational image technique. Learn zsteg, Stegsolve, and manual Python extraction.
- Spectrograms — Visual data hidden in audio. Open Audacity, switch to spectrogram view.
- Whitespace Steganography — SNOW, tab/space encoding, zero-width Unicode.
Intermediate — Deeper Analysis
- PNG Analysis — PNG chunk structure, IHDR dimension tricks, CRC brute-forcing.
- Pixel Manipulation — Channel XOR, alpha hiding, palette tricks, image diff.
- MP3 Steganography — mp3stego, DeepSound, ID3 tag hiding.
- Polyglot Files — Files that are valid in two formats at once.
- Unicode Steganography — Homoglyphs, variation selectors, invisible characters.
Steg by File Type
exiftool image.png # metadata
binwalk -e image.png # embedded files
zsteg image.png # LSB scan (PNG/BMP)
zsteg -a image.png # all LSB combinations
steghide extract -sf image.jpg -p "" # JPEG steghide (blank password)
stegseek image.jpg rockyou.txt # crack steghide password
# java -jar Stegsolve.jar # visual bit plane analysisTool Quick Reference
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