From Halopedia, the Halo wiki
The Beta-3 Division, referred to colloquially as "xenos", is a cell of the Office of Naval Intelligence's Section Three, dedicated to analyzing and replicating alien technology. With the onset of the Human-Covenant War, the division was formed by ONI in an effort to utilize Covenant technology. By March 2526, the division was a fast-growing ONI unit composed of xeno-scientists. In the 2530s, Beta-3 Division was analyzing the workings of Kig-Yar point defense gauntlets.