Pixel Puzzler

1. Python with Pillow and NumPy: pip3 install pillow numpy
2. zsteg (for automatic LSB detection): gem install zsteg (requires Ruby) or download from GitHub
3. Alternative tools: StegSolve (Java-based GUI) or manual hex analysis

1. Download challenge.png from the challenge page to your local machine.
2. Open the image in an image viewer. You will see a random pattern, nothing unusual visually.
3. Use file challenge.png to confirm it's a valid PNG file.
4. Run strings challenge.png | grep -i flag to search for any obvious references to flags in the file.
5. Use exiftool challenge.png to examine metadata for any hidden information.

1. Suspecting steganography, use a tool like zsteg or stegsolve to analyze the image for hidden data.
2. Alternatively, write a Python script using Pillow and numpy to extract the least significant bits from the pixel data.

1. Extract the LSBs from the first len(flag) * 8 pixels of the image.
2. Group the bits into bytes and convert each byte to its ASCII character.
3. The result is the flag: 19d9ad44-709a-40a8-acd6-9ff98cd7b555

1. Install zsteg: gem install zsteg (requires Ruby to be installed)
2. Run the analysis: zsteg challenge.png
3. The output should reveal the flag: 19d9ad44-709a-40a8-acd6-9ff98cd7b555

1. Create a Python script called extract_lsb.py with the following content:

from PIL import Image
import numpy as np

# Load the image
img = Image.open('challenge.png')
arr = np.array(img)

# Flatten the array for easier manipulation
flat = arr.flatten()

# Extract LSBs from the first 36*8 pixels (36 characters * 8 bits each)
bits = []
for i in range(36 * 8):
    bits.append(str(flat[i] & 1))

# Convert bits to bytes and then to ASCII characters
flag = ''
for i in range(36):
    byte_bits = bits[i*8:(i+1)*8]
    byte_value = int(''.join(byte_bits), 2)
    flag += chr(byte_value)

print(f'Extracted flag: {flag}')

2. Run the script: python3 extract_lsb.py
3. The output will be: 19d9ad44-709a-40a8-acd6-9ff98cd7b555

1. Download StegSolve from: https://github.com/zardus/stegsolve
2. Open the challenge.png file in StegSolve
3. Use the 'Analyse' menu to check different channels (Red, Green, Blue, Alpha)
4. Look for the 'LSB' option to view the least significant bits
5. Navigate through the different bit planes to find readable text
6. The flag should appear in one of the LSB views

1. Open the PNG file in a hex editor like HxD, 010 Editor, or hexdump
2. Locate the pixel data section (after the PNG header and metadata)
3. Extract the least significant bit from each byte in the pixel data
4. Group the bits into bytes (8 bits each)
5. Convert each byte to its ASCII character
6. Look for the UUID pattern in the resulting string

• What is LSB Steganography? It's a technique where the least significant bit of each pixel is used to hide data. Since changing the LSB has minimal visual impact, the hidden data is virtually invisible.
• How it works: Each pixel in an RGB image has 3 color channels (Red, Green, Blue), each with 8 bits. The least significant bit of each channel can be modified without significantly affecting the image's appearance.
• Data capacity: For a 100x100 RGB image, you can hide up to 30,000 bits (3,750 bytes) of data in the LSBs.
• Detection: While LSB stego is visually undetectable, statistical analysis can reveal its presence by analyzing the distribution of pixel values.

• LSB Steganography: Hiding data in the least significant bits of image pixels is a common steganography technique used by attackers to exfiltrate data covertly.
• Detection Methods: Automated tools like zsteg, stegdetect, and statistical analysis can detect LSB steganography by analyzing pixel value distributions.
• Security Implications: LSB steganography can be used for covert data exfiltration, hiding malicious code, or communicating secretly. It's often used in advanced persistent threats (APTs).
• Countermeasures: Organizations should scan images for steganography, use network monitoring to detect unusual data patterns, and implement strict file upload policies.
• Forensic Analysis: When investigating security incidents, always check images for hidden data using specialized steganography detection tools.

• Understanding of image file structure and LSB steganography techniques
• Proficiency in using forensic tools for image analysis (zsteg, StegSolve)
• Experience with multiple analysis methods and tools
• Recognition of security implications of hidden data in images
• Development of systematic approach to forensic analysis
• Understanding of how attackers use steganography for data exfiltration
• Knowledge of countermeasures and detection methods