Vehicular Ad hoc Networks (VANET) have emerged as a subset of the Mobile Ad hoc Network (MANET) application; it is considered to be a substantial approach to the Intelligent Transportation System (ITS). VANETs were introduced to support drivers and improve safety issues and driving comfort, as a step towards constructing a safer, cleaner and more intelligent environment. At the present time, vehicles are exposed to many security threats. One of them is the User Datagram Protocol (UDP)- based flooding which is a common form of Denial of Service (DoS) attacks, in which a malicious node forges a large number of fake identities, i.e.-, Internet Protocol (IP) spoofing addresses in order to disrupt the proper functions of the fair data transfer between two fast moving vehicles. Incorporating IP spoofing in the DoS attacks makes it even more difficult to defend against such attacks. In this paper, an efficient method is proposed to detect and defend against UDP flooding attacks under different IP spoofing types. The method makes use of a storage-efficient data structure and a Bloom filter based IPCHOCKREFERENCE detection method. This lightweight approach makes it relatively easy to deploy as its resource requirement is reasonably low. Simulation results consistently showed that the method is both efficient and effective in defending against UDP flooding attacks under different IP spoofing types. Specifically, the method outperformed others in achieving a higher detection rate yet with lower storage and computational costs. © 2013 IEEE.