Transponder

Every space-going vessel possesses a subspace transponder The subspace transponder broadcasts the vessel's registry, hull number, ownership, and other pertinent  information on a special frequency that can be picked up by any vessel or subspace comm array at close range. The transponder also operates as a distress beacon in the  event that a ship suffers some kind of critical emergency. It is considered a serious crime in the Empire to tamper with a transponder in any way, and evidence of an altered  transponder is probable cause enough for a ship to be stopped and boarded by Imperial officers. This doesn't stop those who value their anonymity from doing so, however.