Cyber-Physical Systems Security: a Systematic Mapping Study

Context: Cyber-physical systems (CPS) are integrations of computation, networking, and physical processes. Due to the tight cyberphysical coupling and to the potentially disrupting consequences of failures, security is one of the primary concerns for this type of systems. CPS security is attracting several research efforts from different and independent areas (e.g., secure control, intrusion detection in SCADA systems, etc.), each of them with specific peculiarities, features, and capabilities, resulting in a considerably variegated and complex scientific body of knowledge on the topic. Objective: In this study we aim at identifying, classifying, and analyzing existing research on CPS security in order to better understand how security is actually addressed when dealing with cyber-physical systems. Based on this analysis of the state of the art, we also aim at identifying the implications for future research on CPS security. Method: In order to achieve this, we designed and conducted a systematic mapping study to identify, classify, and compare relevant studies proposing a method or technique for cyber-physical systems security. A comparison framework for classifying methods or techniques for CPS security has been empirically defined; identified relevant studies have been classified on the basis of publication trends, their characteristics and focus, and their validation strategies. Results: We selected a total of 118 primary studies as a result of the systematic mapping process. From the collected data we can observe that (i) even if solutions for CPS security has emerged only recently, in the last years they are gaining a sharply increasing scientific interest across heterogeneous publication venues; (ii) the bulk of the works on security for cyber-physical systems is focused on power grids, and the approaches considering attacks on sensors and their protection completely dominate the scene; regardless of application field and considered system components, all the works on CPS security deal with attacks, in order to either implement or to counteract them, and putting together all this studies gives us the possibility to categorize the existing (cyber-physical) attack models; it comes as surprise that very few papers consider communication aspects or imperfections and attempt to provide non-trivial mathematical models of the communication; (iii) most advanced and realistic validation methods have been exploited in the power networks application domain, but even there a benchmark is still missing. Conclusion: The systematic map of research on CPS security provided here is based on, for instance, application fields, various system components, related algorithms and models, attacks characteristics and defense strategies. This work presents a powerful comparison framework for existing and future research on this hot topic, important for both industry and academia.