# Detecting and Mitigating Attacks on GPS Devices
## 7 Research Gaps, Challenges, and Future Research Directions  
Detecting and mitigating threats to the GPS has recently received significant attention. This paper provides an overview of the environments and attacks in which GPS performance may be degraded or lost. GPS jamming and spoofing attacks are becoming increasingly common, and systems capable of executing these attacks can be readily achieved with low- and no-cost commercial hardware and software components with minimal expertise. The data available in the literature illustrate the commonality of GPS jamming attacks worldwide. Unfortunately, no real-world data were found available for GPS spoofing attacks. A useful measurement campaign would be to establish long-term GPS monitoring sites and pair these sites with some of the advanced GPS spoofing detection approaches found in the literature to determine the frequency of GPS spoofing attacks. Numerous papers in the literature characterize GPS performance. Some of these papers illustrated the performance challenges of GPS in complex multipath and shadowing propagation environments. Some of these papers illustrated the variability in performance across different commercial GPS receivers; however, most of the experiments presented in these papers were not conducted in a controlled manner or with reported rigor. These papers gave a sense of the challenges and performance variability; however, the experimentation methods in most of these papers unfortunately mean that no definitive quantitative conclusions can be drawn from them. Instead, high-level qualitative trends can be inferred from these papers. There are two useful future research activities in this area: (1) controlled and exhaustive experimentation to develop detailed quantitative models of GPSperformance variability across GPS receivers, and (2) controlled experimentation to develop detailed channel models for GPS propagation in complex multipath fading and signal shadowing environments. Furthermore, there is a need for additional research to characterize the performance of GPS receivers in the presence of jamming, such as chirp jamming and partial-band noise jamming. There are a limited number of papers about GPS jamming detection. Most papers focused on two approaches: (1) antenna-based and (2) signal statistics-based. Many of the antenna approaches are promising, but they require antenna arrays that are too large and complex for UAS platforms. Most of the signal statistics-based approaches make simplistic assumptions regarding the propagation environment, and consequently, it is unclear if many of them would perform well in multipath fading or signal shadowing environments. Recent research has employed advanced ML-based approaches for jamming detection and classification. Only a small number of papers in the literature have proposed this approach; however, the results from this limited amount of work are promising. An important future research area would be to expand upon this work and continue maturing ML-based approaches to GPS jammer detection. The topic of GPS spoofing detection has been extensively studied. Consequently, there is a large amount of research on this subject. The most common approach for GPS spoofing detection is ML-based, which has demonstrated strong performance. There is always room for improvement in any technical approach; however, this research topic has matured. Despite the wide range of existing methods and approaches for positioning and navigation in GPS-denied environments, existing methods are either scenario- or environment-specific or have other significant limitations. There are many research opportunities for many of the individual alternate positioning and navigation approaches. Research into self-calibrating multi-IMU approaches is promising, but additional research is required to mature the concept, particularly for harsh environments and platform dynamics. Future research should address the security of using unauthenticated RF landmarks.