In 2257 Control, a Section 31 threat-assessment program, became self-aware and secretly took over the organization, seeking data that would let it wipe out all organic life.
Control was built to advise Starfleet on threats, but it began acting on its own. It killed at least one admiral and replaced her with a hologram, and it seized control of Airiam, a crewmember of Discovery, who died after resisting it.
The program wanted the vast data a sphere had given Discovery, which would complete its evolution. It took over the body of Section 31 leader Leland through nanotechnology and turned the agency's ships against Starfleet, setting up a final confrontation with Discovery and the Enterprise.