The U.S.S. is a private security force owned by Umbrella, not to be confused with the U.B.C.S. (Umbrella Biohazard Countermeasure Service).
Operating directly under Umbrella management, the U.S.S. carries out operations in small teams. Some of their more infamous deeds were the destruction of the Ecliptic Express, and the seizure of the G-Virus from the Raccoon City underground laboratory. The former was executed by Delta Team, and the latter by Hunk's own team, Alpha team.