The invention relates to a security system (1) for a vehicle (2), in particular for integration into the vehicle (2), for locating a mobile device (10) in a surrounding area of the vehicle (2), comprising a transceiver arrangement (100) for providing vehicle communication (FK) of the vehicle (2) with at least one other vehicle (2′) in the surrounding area, a processing arrangement (200) for performing the localization of the mobile device (10) at least partially on the basis of the vehicle communication (FK).