- "There are terrors out there that you can't imagine. But we can. And we do. And the reason we keep our secrets is so all the rest of you can sleep at night, and believe there will be a better world to wake up to tomorrow." - Captain Hu-Lin Radisson.
Project Sign was a secret organization within the United Federation of Planets.
The organization roots are linked to Captain James T. Kirk's first three year voyage on the USS Enterprise after his discovery of a Preserver obelisk as well as the mirror universe. After seeing a number of potential threats though no clear enemy at the time, Starfleet's Technical Intelligence Division created Project Magnet in the year 2275 to serve as a study group. (TOS novel: Preserver)
This eventually led to the creation of Project Sign which was authorised to actively deal with threats to the Federation. In 2374, the agency was noted in tracking the actions of the mirror counterpart of Kirk and the Klingon-Cardassian Alliance began to increase their efforts to cross into the "standard" universe. Seeing this threat manifesting, Project Sign took a more direct tact by aiding the resistance movements in the alternate realm. (TOS novel: Dark Victory)
They were later present at the end of the Preserver's attempt at destroying the mirror universe and aided in helping Emperor Tiberius Kirk return to his home dimension and helping him undo the damage he had done in previous years. They informed Captain Kirk that they would still be out there working to stop threats that were unimaginable to the Federation. (TOS novel: Preserver)
Project Sign's mission was defensive in nature, as it was deemed any active engagement with the parallel reality would be a violation of the Prime Directive. (TOS novel: Dark Victory) However, they worked to combat threats not only from the Mirror Universe but from other threats such as the alien Preservers and even a race of alien parasites of unspeakable power that sought to infiltrate the Federation on at least three occasions. (TOS novel: Preserver)
Project Sign operated from a secret base on Alpha Centauri, and possessed three advanced starships, state of the art medical facilities, and used a great deal of holographic technology. (TOS novel: Dark Victory)