Steganography

A method to hiding something in something.

General

  1. Usually when organizer gave us Image, Music, Video, Zip, EXE, File System, PDF and other files, it a steganography or forensics challenge. Run file command first.

  2. Metadata is important. Checkout the EXIF data of the file by using exiftool [filename] command.

  3. Try issuing binwalk [filename] on the file. They may hide another file in the file.

    • To extract, use binwalk -e.

    • To extract one specific signature type, use binwalk -D 'png image:png' [filename].

    • To extract all files, run binwalk --dd='.*' [filename].

  4. Try file carve using foremost -v [filename] command. Foremost support all files.

Images

  1. View the image first

  2. Use strings command to that file.

    • Try grep -i [any strings you want to filter] from the strings command output.

    • Example grep -i "flag{" to filtering the flag format only. -i option to unable case sensitive.

  3. Google the images, differentiate the md5hash. If you found same image but have a different md5 hash, it may probably have been altered.

  4. Analyse the header and the content of the file using any hex editor.

  5. Know the file signature. Maybe they gave us corrupt header! So fix it!

  6. Maybe zoom-in and zoom-out method can get the flag.

  7. Use https://www.tineye.com/ to reverse search the image in the internet.

  8. Use imagemagick command tool to do image manipulation.

  9. Use Stegsolve.jar tools. There are so many CTF I've participated that I used this tool to unhide flag from an image.

  10. File carve using steghide --extract -sf <filename>. Try find the password with your own-self. Maybe, the organizer will give hints or the password may in another file.

  11. Check for any corruption on PNG file by using pngcheck <filename.png> command.

  12. Detect stegano-hidden data in PNG & BMP s by issuing zsteg -a <filename.png>.

  13. Use SmartDeblur software to fix blurry on image.

  14. Use stegcracker <filename> <wordlist> tools Steganography brute-force password utility to uncover hidden data inside files.

  15. Use tesseract to scan text in image and convert it to .txt file.

  16. Another powerfool tool is called zsteg.

Compressed file

  1. Unzip it.

    1. Use zipdetails -v command to display details about the internal structure of a Zip file.

    2. Use zipinfo command to know details info about Zip file.

    3. Use zip -FF input.zip --out output.zip attempt to repair a corrupted zip file.

    4. Brute-force the zip password using fcrackzip -D -u -p rockyou.txt filename.zip

  2. To crack 7z run 7z2hashcat32-1.3.exe filename.7z. Then john --wordlist=/usr/share/wordlists/rockyou.txt hash

Music file

  1. Use binwalk first. They may embedded something in the file.

  2. Use Audacity.

  3. Use Sonic Visualizer. Look at spectogram and other few Pane.

  4. Use Deepsound.

  5. Use SilentEye.

  6. Some of online stegano decoder for music:-

Text

  1. Use http://www.spammimic.com/ that can decode hide message in spam text.