SD-6 (Section Disparu, "the section which has disappeared") was a branch of the Alliance of Twelve run by Arvin Sloane under the pretense of being a black-ops division of the CIA. In reality, the cell was one of over 100 SD-cells that operated on behalf of the Alliance of Twelve. They were working against the U.S. government. After months of undercover work with the real CIA, agents Jack and Sydney Bristow eventually managed to take down SD-6 along with all other branches of the Alliance.