# Detecting and Mitigating Attacks on GPS Devices
## 2 Existing Surveys  
Several surveys related to GPS performance, GPS security, and navigation and positioning in GPS-denied and GPS-disrupted environments can be found in the literature. Table 1 lists recent surveys related to positioning and navigation in GPS-denied environments, emphasizing UAS applications, and specifies the topics covered and not covered by each of these surveys. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Survey Paper**} & \multicolumn{4}{c}{**Topics Covered**} & \multicolumn{4}{c}{**Specific Topics**} \\ \cline{2-7}  & **Attacks** & **Detection** & **Mitigations** & **GPS Spoofing** & **GPS Jamming** &
\begin{tabular}{c} **Alternative (Non-GNSS)** \\ **Positioning and Navigation** \\ \end{tabular} \\ \hline  
Our paper & X & X & X & X & X & X \\ \hline \hline \end{tabular}
\end{table} 
Table 1: High-level summary of the existing research on the topic of GPS security and alternate positioning. These surveys are analyzed in terms of (1) type of attack, (2) attack detection method, and (3) attack mitigation approaches. The papers were categorized according to the final topics: (1) GPS spoofing, an attack type where a malicious actor attempts to broadcast a falsified GPS signal to trick a receiver into calculating an incorrect position; (2) GPS jamming, an attack type where a malicious actor attempts to broadcast an interference signal to prevent a receiver from properly receiving the actual GPS signal; or (3) alternative (non-GNSS) positioning and navigation, such as positioning methods in GPS-denied environments. The authors of [1; 2; 3; 4] provided a holistic review of literature focused on the UAS cybersecurity space, encompassing general aspects related to UAS cybersecurity, including GPS jamming and spoofing. They also analyzed the overall cybersecurity challenges facing unmanned systems, covering a broad range of threats to the various sub-systems that comprise these systems. The authors of [5] provided a comprehensive overview of jamming attacks and mitigation strategies across a wide range of wireless technologies, including GPS receivers. The authors of [6] focused on GPS jamming, summarizing different types of attacks and mitigation approaches. The authors of [7] presented a comprehensive review of unintentional and intentional threats against GNSS systems, focusing on GPS, discussing various degradation mechanisms, attacks against the GPS system, and many types of mitigations. The authors of [7] assessed the impacts of various types of degradation in terms of accuracy, integrity, availability, and continuity. Mitigation strategies were analyzed in terms of performance, cost, and complexity. The authors of [8; 9; 10] presented comprehensive reviews of GNSS spoofing threats, focusing on GPS. There is overlap between these surveys in the approaches they summarize, but they use different attack and mitigation taxonomies, which reflect slightly different foci between these papers. The authors of [8] proposed a taxonomy of spoofing mitigation methods consisting of (1) signal processing-based methods, (2) encryption-based methods, (3) correlation-based methods, and (4) antenna-based methods. The authors of [9] used a different spoofing mitigation taxonomy, dividing approaches into (1) signal processing-based approaches, (2) encryption-based approaches, (3) drift monitoring-based approaches, (4) signal geometry-based approaches, and (5) multi-pronged spoofing defense approaches. The authors of [10], primarily considering UAS applications, focus primarily on different types of GPS attacks. However, the authors of [10] provide a summary of many methods to make receivers robust against spoofing attacks, including a variety of approaches based on GPS signal characteristics and the perceived source location of the GPS signal. The authors of [10] also discuss the potential benefits of multi-GNSS receivers to mitigate GPS spoofing attacks.