A System Theoretic Approach to Cybersecurity Risk Analysis and Mitigation for Autonomous Passenger Vehicles

Abstract

Urban Mobility is in the midst of a revolution, driven by the convergence of technologies such as artificial intelligence, on-demand ride services, as well as connected and self-driving vehicles. Technological advancements often lead to new hazards and changing nature in how accidents can happen. Coupled with the increased levels of automation and connectivity in the new generation of autonomous vehicles, cybersecurity is emerging as one of the key threats affecting the safety of these vehicles. Traditional hazards analysis methods treat safety and security in isolation, and are limited in their ability to account for interactions among organizational, socio-technical, human, and technical components. In response to these challenges, the System Theoretic Process Analysis (STPA) was developed to meet the growing need for system engineers to holistically analyze complex socio-technical systems. We applied STPA-Sec, an extension to STPA to include security analysis, to co-analyze safety and security hazards, as well as identify mitigation requirements. The results were compared with another promising method known as Combined Harm Analysis of Safety and Security for Information Systems (CHASSIS). Both methods were applied to the Mobility-as-a-Service use case, focusing on over-the-air software updates feature. Overall, STPA-Sec identified additional hazards and more effective requirements compared to CHASSIS. In particular, STPA-Sec demonstrated the ability to identify hazards due to unsafe/ unsecure interactions among sociotechnical components. This research also suggested using CHASSIS methods for information lifecycle analysis to complement and generate additional considerations for STPA-Sec. Finally, results from both methods were back-tested against a past cyber hack on a vehicular system, and we found that recommendations from STPA-Sec were likely to mitigate the risks of the incident.