steganography-techniques

# pngcheck — validate structure, find hidden chunks
pngcheck -v image.png
 
# Hidden chunks: tEXt, zTXt (compressed text), iTXt (international text)
# Custom/private chunks may contain hidden data
 
# CRC vs dimensions trick
# If CRC doesn't match declared dimensions → image was cropped
# Fix: brute-force correct width/height → reveals hidden rows/columns
python3 -c "
import struct, zlib
with open('image.png','rb') as f:
    data = f.read()
# Check IHDR CRC at offset 29
ihdr = data[12:29]
for h in range(1,2000):
    for w in range(1,2000):
        new_ihdr = struct.pack('>II',w,h) + ihdr[8:]
        if zlib.crc32(b'IHDR'+new_ihdr) & 0xffffffff == struct.unpack('>I',data[29:33])[0]:
            print(f'Width: {w}, Height: {h}')
"
 
# APNG (animated PNG) — hidden frames
# Use apngdis to extract all frames: apngdis image.png

# steghide — embed/extract from JPEG (DCT coefficient modification)
steghide extract -sf image.jpg                 # extract (no passphrase)
steghide extract -sf image.jpg -p PASSWORD     # extract with passphrase
steghide info image.jpg                        # check if data is embedded
 
# stegcracker — brute force steghide passphrase
stegcracker image.jpg wordlist.txt
 
# jsteg — JPEG LSB steganography
jsteg reveal image.jpg output.txt
 
# JPEG structure analysis
exiftool -v3 image.jpg       # verbose metadata + structure
jpegdump image.jpg           # raw JPEG marker analysis

# exiftool — comprehensive metadata extraction
exiftool image.jpg
exiftool -b -ThumbnailImage image.jpg > thumb.jpg   # extract thumbnail
exiftool -all= image.jpg                             # strip all metadata
 
# Hidden data in EXIF fields (comment, artist, copyright, etc.)
exiftool -Comment image.jpg
exiftool -UserComment image.jpg
strings image.jpg | grep -i "flag\|key\|secret"

# GIF color table manipulation — data in color palette order
gifsicle -I image.gif                    # info
gifsicle --color-info image.gif          # palette details
# Check for animation frames: convert -coalesce image.gif frame_%d.png

# Sonic Visualiser — best for spectrogram viewing
# Layer → Add Spectrogram → look for visual patterns (text/images)
 
# Audacity
# Analyze → Plot Spectrum
# Select audio → change view to Spectrogram
 
# sox for command-line spectrogram generation
sox audio.wav -n spectrogram -o spectro.png

# DeepSound — hide/extract files in audio (Windows)
# GUI tool: open audio file → extract hidden files
 
# WavSteg — LSB in WAV files
python3 WavSteg.py -r -i audio.wav -o output.txt -n 1   # extract 1 LSB
python3 WavSteg.py -r -i audio.wav -o output.txt -n 2   # extract 2 LSBs

# DTMF decoder (phone tones)
multimon-ng -t wav -a DTMF audio.wav
 
# Morse code
# Audacity → visual inspection of on/off pattern
# Online decoder or manual: .- = A, -... = B, etc.
 
# SSTV (Slow-Scan Television) — image in audio
qsstv                    # GUI decoder
# Or: RX-SSTV (Windows)

# Check for data appended after WAV audio data
# WAV data chunk size vs actual file size
python3 -c "
import wave
w = wave.open('audio.wav','rb')
print(f'Frames: {w.getnframes()}, Channels: {w.getnchannels()}, Width: {w.getsampwidth()}')
expected = w.getnframes() * w.getnchannels() * w.getsampwidth() + 44  # 44 = WAV header
import os
actual = os.path.getsize('audio.wav')
if actual > expected:
    print(f'Extra data: {actual - expected} bytes appended')
"

# Detection: check file with multiple tools
file suspicious_file
xxd suspicious_file | head          # check magic bytes
binwalk suspicious_file             # find embedded files
 
# Common polyglots: PDF+ZIP, JPEG+ZIP, JPEG+RAR, PNG+ZIP
# Try unzip on image files:
unzip image.jpg -d extracted/
7z x image.jpg -oextracted/

# binwalk — scan for embedded files and data
binwalk image.png                   # scan
binwalk -e image.png                # extract embedded files
binwalk --dd='.*' image.png         # extract everything
 
# foremost — file carving
foremost -i suspicious_file -o output_dir/
 
# dd — manual extraction
# If binwalk shows embedded ZIP at offset 0x1234:
dd if=suspicious_file bs=1 skip=$((0x1234)) of=extracted.zip

:: List ADS (Windows)
dir /r file.txt
Get-Item file.txt -Stream *
 
:: Read hidden stream
more < file.txt:hidden_stream
Get-Content file.txt -Stream hidden_stream
 
:: Create ADS (for testing)
echo "hidden data" > file.txt:secret

# stegcracker — wordlist attack on steghide passphrase
stegcracker image.jpg /usr/share/wordlists/rockyou.txt
 
# stegseek — faster alternative
stegseek image.jpg /usr/share/wordlists/rockyou.txt
# stegseek is ~10000x faster than stegcracker

# Tabs and spaces encode binary (tab=1, space=0 or vice versa)
# stegsnow — whitespace steganography
stegsnow -C message.txt                # extract hidden message
stegsnow -C -p PASSWORD message.txt    # extract with password
 
# Manual detection:
cat -A file.txt | head     # show tabs (^I) and line endings ($)
xxd file.txt | grep "09 20\|20 09"    # look for tab/space patterns

# Unicode invisible characters used for encoding:
# U+200B (Zero-Width Space), U+200C (ZWNJ), U+200D (ZWJ), U+FEFF (BOM)
 
# Detection:
python3 -c "
text = open('message.txt','r').read()
hidden = [c for c in text if ord(c) in [0x200b, 0x200c, 0x200d, 0xfeff]]
print(f'Found {len(hidden)} zero-width characters')
binary = ''.join('0' if ord(c)==0x200b else '1' for c in hidden)
# Convert binary to ASCII
"
 
# Online tools: holloway.nz/steg, Unicode Steganography decoders

# Visually identical characters from different Unicode blocks
# e.g., Latin 'a' (U+0061) vs Cyrillic 'а' (U+0430)
 
# Detection:
python3 -c "
text = open('message.txt','r').read()
for i, c in enumerate(text):
    if ord(c) > 127:
        print(f'Position {i}: char={c} ord={ord(c)} name={__import__(\"unicodedata\").name(c,\"?\")}')
"

Suspect hidden data — what file type?
│
├── Image (PNG/BMP)?
│   ├── Check metadata: exiftool (§1 EXIF)
│   ├── Check structure: pngcheck, binwalk (§1 PNG)
│   ├── LSB analysis: zsteg, StegSolve (§1 LSB)
│   ├── Check dimensions vs CRC: height/width brute force (§1 PNG)
│   ├── Check for appended data: binwalk -e (§3)
│   └── Try as polyglot: unzip/7z (§3)
│
├── Image (JPEG)?
│   ├── Check metadata: exiftool (§1 EXIF)
│   ├── Try steghide: steghide extract (§1 JPEG)
│   │   └── Password protected? → stegseek brute force (§3)
│   ├── Try jsteg: jsteg reveal (§1 JPEG)
│   ├── Check for appended data: binwalk -e (§3)
│   └── Check thumbnail: exiftool -b -ThumbnailImage (§1 EXIF)
│
├── Image (GIF)?
│   ├── Check frames: extract all animation frames (§1 Palette)
│   ├── Check palette: gifsicle --color-info (§1 Palette)
│   └── Check for appended data: binwalk -e (§3)
│
├── Audio (WAV/MP3/FLAC)?
│   ├── Spectrogram: Sonic Visualiser / Audacity (§2)
│   ├── LSB: WavSteg (§2)
│   ├── DTMF tones: multimon-ng (§2)
│   ├── Morse code: manual or decoder (§2)
│   ├── SSTV: qsstv (§2)
│   └── Check file size vs expected: header analysis (§2)
│
├── Text file?
│   ├── Check whitespace: cat -A, stegsnow (§4)
│   ├── Check zero-width chars: Unicode analysis (§4)
│   ├── Check homoglyphs: non-ASCII detection (§4)
│   └── Check encoding: multiple base decodings
│
├── Any file type?
│   ├── strings: strings -n 8 file | grep -i "flag\|key\|pass"
│   ├── binwalk: binwalk -e file (embedded files) (§3)
│   ├── file: file suspicious_file (true type)
│   ├── xxd: check magic bytes, compare headers
│   └── NTFS? → check ADS: dir /r (§3)
│
└── Password/passphrase needed?
    ├── steghide → stegseek / stegcracker (§3)
    ├── Check challenge description for hints
    └── Try common passwords: password, file name, challenge name