The evolving of Fifth Generation (5G) networks is becoming more readily available as a significant driver of the growth of new applications and business models. Vehicular Ad hoc Networks (VANETs) and Software Defined Networking (SDN) represent the critical enablers of 5G technology with the development of next-generation intelligent vehicular networks and applications. In recent years, researchers have focused on the integration of SDN and VANET, and looked at different topics related to the architecture, the benefits of software-defined VANET services, and the new functionalities to adapt them. However, the security and robustness of the complete architecture is still questionable and have been largely neglected by the research community. Moreover, the deployment and integration of different entities and several architectural components drive new security threats and vulnerabilities.

In this paper, first, we survey the state-of-the-art SDN based Vehicular ad-hoc Network (SDVN) architectures for their networking infrastructure design, functionalities, benefits, and challenges. Then we discuss these architectures against major security threats that violate the key security services such as availability, privacy, authentication, and data integrity. We also discuss different countermeasures for these threats. Finally, we present the lessons learned with the directions of future research work towards provisioning stringent security solutions in new SDVN architectures. To the best of our knowledge, this is the first work that presents a comprehensive survey and security analysis on SDVN architectures, and we believe that it will help researchers to address various challenges (e.g., flexible network management, control and high resource utilization, and scalability) in vehicular communication systems which are required to improve the future Intelligent Transportation Systems (ITS).