We consider a scenario where we use multiple GPS receivers to detect the presence of spoofer(s). The GPS receivers are fixed on a rigid body so their relative mutual distances are fixed during the detection process. We consider a sophisticated spoofing attack in this work. In a sophisticated attack, there are multiple spoofers in the environment where their clocks are synchronized. Each of the spoofers receives the signal of a specific GPS satellite, modifies the ephemeris data of the satellite and retransmits it.
When the adversaries want to spoof the location of five or more GPS receivers, there exists only one possible point for each spoofer to mount the attack such that the relative distances of the GPS receivers remain unchanged. However, in practice, it may not be possible for each spoofer to be in the required location at each moment so that the spoofers always keep their unique formation in the space. This is due to the fact that the GPS receivers are installed on a moving platform and physical limits as well as unknown velocity and speed can prevent the spoofers to fill the required position. Based on the mentioned difficulties for the spoofer, here, we consider the case where the spoofers fail to occupy the desired positions in the space. Therefore, they cannot spoof the location of the GPS receivers while maintaining their formation. In other words, the relative distance of the GPS receivers changes under spoofing. This work focuses on exploiting this opportunity to detect the presence of spoofers.