Recently, software defined networks have been introduced for innovation and flexibility in computer networks. They are widely used in infrastructure networks and data centers. Using these networks has advantages such as scalability, efficient bandwidth usage, reducing control traffic, better traffic engineering and etc., which are mainly due to their programmability. There are also some security challenges that often arise from the same property. Software defined networks reliability compared to traditional network reduces due to these challenges. Therefore, if software defined networks are not design based on a security architecture, they will be vulnerable against known cyber-attacks such as DDoS, spoofing, information disclosure and etc. In this paper, software defined network security challenges and corresponding solutions are reviewed. Moreover, some applications of software defined networks for security including network traffic separation, network flow access control, and secure routing are mentioned. In order to do security testing and evaluation of relevant security solutions we have explained how these networks are simulated.