Dedicated Short Range Communications (DSRC) enabled road vehicles are on the brink of actualizing an important application of mobile ad hoc networks. It is crucial that the messages exchanged between the vehicles and between the vehicles and specialized infrastructure be reliable, accurate and confidential. To this end, we propose to identify the security threats inherent in the emerging DSRC Wireless Access in Vehicular Environments (WAVE) architecture. We rank the identified threats according to the European Telecommunications Standards Institute's (ETSI) threat analysis methodology. We also discuss possible countermeasures to the most critical threats.