A common countermeasure that attacking parties use to disrupt the efficacy of Missile Defense Systems are the simultaneous launching of decoys from the primary launch site or from the exterior of the main attacking missile itself. These decoys are usually small, lightweight dud rockets that take advantage of the interceptor sensors tracking and fool it by making many different targets available in an instant, This accomplished via the releasing of decoys in certain phases of flight. Because objects of differing weights follow the same trajectory when in space, decoys released during the midcourse phase can prevent interceptor missiles from accurately identifying the warhead. This could force the defense system to attempt to destroy all incoming projectiles, which masks the true attacking missile and lets it slip by the defense system.