Section 31
Section 31 is a covert Federation intelligence agency first seen in DS9 "Inquisition". It's existence is largely unknown to Federation citizens.
Functions
Section 31 handles intelligence gathering and covert operations that violate the Starfleet charter and Federation law. The operation for which they are best known is the invention and deployment of a biological weapon for a genocide attack against the Founders of the Dominion. Section 31 existed before NX Enterprise was send on it legacy journey.