Automotive industries are maximizing cooperative interactions between vehicular sensors and infrastructure components to make intelligent decisions in its application (i.e traffic management, naviga- tion, or autonomous driving services). This cooperative behaviour also extends to security. With more connected and cooperative components of vehicular intelligent transportation systems (ITS), the possibility of malicious attacks against ITS ecosystem become highly visible, produc- ing risks with high security and safety impact. The security risks in one architecture layer impacts other layers of ITS, thus, cooperation for these systems to be securely operated is essential. This paper presents results from a comprehensive literature analysis on the state-of-the-art of security risk management in vehicular ITS, evaluating its assets, threats/risks and countermeasures. We examine these security elements along the dimensions of the perception, network and application architecture layers of ITS. The study reveals gaps in ITS security risk management research within these architecture layers and provides a proposition for future research.