In this search, we provide a study about the security in VANET networks which are considered to be a part of mobile wireless networks and designed to work between moving vehicles. The most important security flaws of this networks and its applications are studied. In fact, we study the most important and dangerous attacks that may target VANET networks and analyze its main risks. Furthermore, we simulate some of these attacks Specifically Denial-of Service (DOS) attack using prober tools depending on chosen parameters that characterize the network performance. moreover, we provide some Security solutions to help counter measuring these attacks and minimize this effects, and Finally we apply these solutions and evaluate them.