Autonomous vehicles (AVs) represent a transformative shift in transportation, promising faster transit, enhanced safety, and reduced accidents. Leveraging the Vehicular Ad-Hoc Network (VANET) for communication among vehicles and roadside units, AVs exchange critical information to optimize driving conditions. However, the constant communication necessitates robust security measures to safeguard both the network and the vehicles themselves. This paper delves into the various cyber threats facing AVs and proposes countermeasures to mitigate them. A comparative analysis identifies prevalent attacks such as Denial of Service (DoS), Sybil, Spoofing, Replay, and Blackhole attacks as the most prominent in AV environments. Subsequently, protocols aimed at thwarting these common attacks are examined. However, it is noted that these protocols may fall short in cases where physical tampering compromises the vehicle’s systems. To address this vulnerability, a novel countermeasure involving cryptographic key management for system access control is proposed and discussed. Additionally, the reliability of each countermeasure is evaluated to ensure robust protection against evolving threats.