VEHICULAR AD HOC NETWORK (VANET) IS A DYNAMIC NETWORK TOPOLOGY WITH WIRELESS MEDIA INFRASTRUCTURE. IN ADDITION VEHICULAR AD HOC NETWORK, ACCESS TO SAFETY AND ENTERTAINMENT PROGRAMS IS PROVIDED ON THESE NETWORKS. SUCH AS INFORMATION ON ROAD CONDITIONS, TRAFFIC CONDITIONS, CRASH REPORTS, AND MORE… , AND THIS VARIETY HAS BECOME MORE DEVELOPMENT THE VEHICULAR AD HOC NETWORK. SINCE THE SECURITY OF THESE NETWORKS IS INVOLVED WITH EVERYDAY LIFE AND EVEN HUMAN LIVES, SO ONE OF THE MAJOR STUDIES IN THE DEVELOPMENT OF THE INTELLIGENT TRANSPORTATION SYSTEM (ITS) IS TO CHECK THE SECURITY OF THESE NETWORKS. DUE TO THE FEATURES OF THIS NETWORK, SUCH AS BANDWIDTH RESTRICTIONS, PERMANENT INFORMATION EXCHANGE, NEED TO RESPOND TIMELY AND MORE, CERTAIN SECURITY ARCHITECTURES SHOULD BE CONSIDERED. IN THIS PAPER, THE SECURITY REQUIREMENTS OF THESE NETWORKS AND IMPORTANT OF ATTACKS IN VARIOUS AREAS HAVE BEEN STUDIED. MOREOVER SEVERAL SECURITY MECHANISMS AND CHALLENGES HAVE BEEN STUDIED.