Cicada 3301: An Anonymous Recruitment System Disguised as a Cipher Game

On January 4, 2012, an account named 3301 posted an image of a cicada on the 4chan forum. The text in the image said the group was looking for very smart people. Anyone who downloaded the image found hidden data inside it. To continue, solvers had to crack ciphers, read books, call a telephone number, find GPS coordinates, and track down QR-code posters in cities around the world.

This was not an ordinary online puzzle. Solvers had to use steganography, the technique of hiding information inside a file that looks completely ordinary. They needed Caesar ciphers, book codes, Linux, Tor, and digital signature checking. When the puzzle led out onto city streets, they also had to work with people in other time zones. At the same time, an anonymous group had prepared online material, phone numbers, servers, and physical posters.