Software Defined Networking (SDN) is a new paradigm that allows for greater reliability and more efficient management compared to traditional networks. However, SDN security is a developing field, and research towards fixing significant security vulnerabilities is still ongoing. One major threat to SDN security are attacks that seek to exploit policy and flow rule enforcement. This paper aims to summarise how these attacks are conducted and the weaknesses they target. Then, state-of-the-art solutions to these weaknesses will be presented, along with their use cases, advantages and disadvantages. Finally, an improvement on the state-of-the-art solutions will be proposed, as well as a potential direction for future research.