The boom in the evolution and adoption of new technologies, architectures, and paradigms such as cloud computing, SDN, and NFV in recent years has led to a new set of security and privacy challenges and concerns. These challenges/ concerns include proper authentication, access control, data privacy, and data integrity, among others. SDP has been proposed as a security model/framework to protect modern networks in a dynamic manner. This framework follows a need-to-know model where a device's identity is first verified and authenticated before gaining access to the application infrastructure. In this article, a brief discussion of the security and privacy challenges/concerns facing modern cloud-based networks is presented along with some of the related work from the literature. The SDP concept, architecture, possible implementations, and challenges are described. An SDP-based framework adopting a client-gateway architecture is proposed with its performance being evaluated using a virtualized network testbed for an internal enterprise scenario as a use case. To the best of our knowledge, no previous work has provided a quantitative performance evaluation of such a framework. Performance evaluation results show that the SDP-secured network is resilient to denial of service attacks and port scanning attacks despite needing longer initial connection setup time. The achieved results confirm the promising potential of SDP as a security model/framework that can dynamically protect current and future networks.