Historically, cybersecurity has been mainly considered for software of computer systems and networks. In recent years, the number of electronic control units (ECUs) in modern vehicles, as well as the amount of software and importance of software used in vehicles, has been increasing. Modern vehicles contain up to 100 ECUs, which are connected to fulfill their respective functions.1 Many of these ECUs are safety related, such as airbag control, adaptive cruise control, and the braking system. Because ECUs within a vehicle are interconnected, the security of the safety-related ECUs depends strongly on the security of the other ECUs. Cybersecurity needs to expand to include vehicles.