Computer Network is a collaboration platform for digital gadgets. Virtualization is abstracting layers from underlying Architecture. Virtualization platform provides flexibility, green resource usage and fast deployment of the carrier. Integration of Computer Network and Virtualization Platform Create Network Virtualization Platform. Software-Defined Network (SDN) Provide dynamic and scalable networking offerings to Business Environments Cloud Network and Data Centers. SDN is controlling network infrastructure with the control plane. Security is a challenging problem for the network. SDN comes with Network Programmability and automation. SDN has an advantage, but it contains a new safety issue. SDN is focused on network safety data plane and control. Security Challenges in SDN is Control Plane, Data Plane Attacks. In Controller Layer Attacker at controller Layer, an routing, visitors filtering denying, or allowing unnecessary site visitors. Control plane assault used to drop or lack of manage over traffic policy and Quality of carrier control. Data Plane Attack Attacker can create DOS Denial of Service.