"Hello. We are looking for highly intelligent individuals. To find them, we have devised a test. There is a message hidden in this image. Find it, and it will lead you on the road to finding us. We look forward to meeting the few that will make it all the way through. Good luck."
That message, signed "3301," appeared on the underground message board known as 4chan two years ago. It was mysterious, cryptic and sparked a global Internet mystery that has yet to be answered to this day.