Impact of GPS Time Spoofing Attacks on Cyber Physical Systems

The development of software defined radio platforms and related open source software have made it possible to generate and broadcast global positioning system (GPS) signals easily and at low cost. Since GPS time is widely used in time sensitive systems for time reference, any attack on GPS can have serious consequences. This paper evaluates GPS time spoofing attacks in cyber physical systems. We explore methods to spoof the GPS time by manipulating the GPS timestamp or the signal propagation time of GPS satellite signals. In our experiments, the impact of GPS time spoofing attacks on the pseudorange, receiver location, and time errors is investigated. Our results show that when only the GPS timestamp is changed or the same delay is introduced to all signals, the resulting location error and pseudorange error can be very small, making it difficult to detect. In particular, the attacks achieved by inserting the same delay have constant location error and negligible pseudorange error. Conversely, the attacks that insert different delay to each signal or change the GPS timestamp at the same time usually lead to large location error and pseudorange error that are easy for attack detection. Moreover, the attacks that change the propagation time are difficult to distinguish irrespective of whether it can cause enough damage to violate the IEEE C37.118 standard or not.