# Prevention of Controller Area Network (CAN) Attacks on Electric Autonomous Vehicles
## 2 CAN Bus Attacks  
Although modern vehicles are reliant on CAN buses in internal ECU communication, CAN buses possess multiple security vulnerabilities, such as the deficiency in network segmentation, the lack of device authentication, and the absence of data encryption. These vulnerabilities can be exposed by attackers to gain access to confidential data, alter the vehicle functionality, and possibly endanger the targeted vehicle's driver and passengers. Attackers target vehicle CAN buses through attacks such as sniffing attacks, fuzzing attacks, frame falsifying attacks, injection attacks, DoS attacks, and ECU impersonation [1]. Some of the mentioned attacks, if performed successfully on a vehicle, can unlock other attacks on other vehicles with the same CAN architecture. For example, an attacker can use sniffing attacks to gain access to CAN bus confidential messages' specifications. The attacker then can use those specifications to manipulate and generate confidential messages [2], unlocking other attacks such as frame falsifying attacks and injection attacks. Another example is attackers using fuzzing attacks to discover possible vulnerabilities in the CAN system that are not yet known to the manufacturer, leading to zero-day attacks [3]. The most common CAN attacks are summarized in Table 1.  
Attackers could gain access to the CAN bus through two attack paths. The first attack path, as shown in Figure 1, is carried out by injecting a malicious code into an ECU that is connected to the CAN bus, which the attackers can use to sniff on the network and to inject their attacks. The second attack path, as shown in Figure 2, is carried out by connecting a malicious external ECU to the network and using that malicious ECU to perform the \begin{table}
\begin{tabular}{c c c} \hline \hline
**CAN Bus Attack** & **Exploited Vulnerabilities** & **Unlock Attacks on Other Vehicles** \\ \hline Sniffing attacks & Absence of segmentation & Yes \\  & Absence of data encryption & \\ \hline Fuzzing attacks & Absence of segmentation & Yes \\  & Absence of authentication & No \\ \hline Injection attacks & Absence of segmentation & \\  & Absence of authentication & Yes \\  & Absence of data encryption & \\ \hline DoS attacks & Absence of segmentation & No \\ \hline ECU impersonation & Absence of authentication & Yes \\  & Absence of data encryption & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: CAN bus attacks, the vulnerabilities that each attack exploits, and whether a successful attempt of an attack on a vehicle could unlock the same attack or other attacks on other vehicles. attacks. Between these attack paths, the first path imposes more threat because it is scalable to other vehicles, and it does not require physical access to the vehicle as malicious code injection could occur remotely [4; 5]. As an example of the first attack path, the authors of [6] injected a code that monitors vehicle behavior, and if a specified condition occurs, it sends a CAN message containing an open window command to open the window. In [4], a personal computer (PC) attached to a powertrain network was used to demonstrate the danger of interfering with the CAN bus. The attached PC, which is an example of an added malicious ECU in the second attack path, interfaced with the CAN bus to falsify the presence of the airbag system when it was removed. The literature contains various other attacks targeting the CAN bus. In [7], experiments were conducted to demonstrate that malicious access to the CAN bus can lead to the attackers taking control over critical components of the targeted vehicle, such as the brakes. Ref. [8] performed a DoS attack by occupying the CAN bus with high-priority messages sent at high frequencies. Ref. [9] used a spoofing attack to impersonate a targeted ECU and caused an error that caused the targeted ECU to be disconnected from the network. In [10], the authors were able to use the Wi-Fi hotspot and the cellular network interface of the 2014 Jeep Cherokee to remotely access its CAN bus.