Outguess is a steganography tools that allows a user to embedd hidden data inside of a JPEG-image file (and some other image formats). It stores the data by modifying redundant information, so that it doesn't cause visual changes to the image. Outguess became widely known since Cicada 3301 posted their first image on 4chan in 2012. The image contained a hidden message that lead the reader to their recruitment tests.

Linux installation

Outguess is available as a package for the most popular Linux distributions. For example in Debian or Ubuntu you install it with this command:

    sudo apt-get update
    sudo apt-get install outguess

If your Linux distribution doesn't have a Outguess package, you can download the source code and follow the instructions in the README file provided.

Windows installation

While there are executables available for Windows, they are not fully compatible with the Linux version. Instead you can install Cygwin (an environment that runs under Windows but is similar to Linux) and use the outguess package provided there.

  • Download Cygwin
  • Make sure you use the 32-bit version. Outguess doesn't work in the 64-bit version.
  • During the installation, on the page "Select Packages", make sure to include Outguess. Type outguess in the search field to find it.