The aim of this research is to develop an enhanced reference monitor algorithm for Software Defined Networking (SDN) controller for 5G security. It is anticipated that by 2025, the network infrastructure should be able to provide connectivity for almost everything. This is expected to bring over 50 billion connections which cannot be handled by the current 4G. While 4G networks main focus is ubiquitous mobile broadband, 5G technology characteristics will have to increase immensely. The flexibility provided by software is key to meeting the unforeseen future service requirement. In this regard, Software Defined Networking (SDN) has recently gathered momentum in the networking industry and specific standard is yet to be adopted on how to check security challenges on SDN for 5G. This work proposes to adopt 5-ENSURE framework of integrating Reference Monitor (RM) to SDN controllers in order to impose access control policy. The Study will also isolate and handle malicious packets in a distributed manner among nodes rather than only permitting or denying access based on access policy. This work would contribute in security standardization of SDN for 5G which is currently under study across the world.