Vehicular Network is an emerging and developing technology to improve traffic management and safety issues, and enable a wide range of value-added services such as collision warning/avoidance. Many applications have been designed to provide safety and comfort for passengers. This technology is a prolific area for attackers who will attempt to challenge the network with their malicious or rational attacks. In this paper we elaborate what a vehicular network is, different kinds of communication in this field, main mechanism and related parts and how vehicular networks work then we introduce some of its applications. After primary familiarity with this system we investigate to different type of attacker, more important security issues, How to secure vehicular networks (security requirements and some tools and methods to achieve secure vehicular networks), difficulties and providing viable security solutions, and at the end briefly explanation of related standards.