Modern vehicles contain multiple interfaces—connections between the vehicle and external networks—that leave vehicle systems, including safety-critical systems, such as braking and steering, vulnerable to cyberattacks. Researchers have shown that these interfaces—if not properly secured—can be exploited through direct, physical access to a vehicle, as well as remotely through shortrange and long-range wireless channels. For example, researchers have shown that attackers could compromise vulnerabilities in the short-range wireless connections to vehicles’ Bluetooth units—which enable hands-free cell phone use—to gain access to in-vehicle networks, to take control over safety-critical functions such as the brakes. Among the interfaces that can be exploited through direct access, most stakeholders we spoke with expressed concerns about the statutorily mandated on-board diagnostics port, which provides access to a broad range of vehicle systems for emissions and diagnostic testing purposes. However, the majority of selected industry stakeholders we spoke with (23 out of 32) agreed that wireless attacks, such as those exploiting vulnerabilities in vehicles’ built-in cellular-calling capabilities, would pose the largest risk to passenger safety. Such attacks could potentially impact a large number of vehicles and allow an attacker to access targeted vehicles from anywhere in the world. Despite these concerns, some stakeholders pointed out that such attacks remain difficult because of the time and expertise needed to carry them out and thus far have not been reported outside of the research environment.