The ever-growing volume of network traffic and widening adoption of Internet protocols to underpin common communication processes augments the importance of network security. In order to enforce network security policies, network managers adopt a widening set of middleboxes and network appliances to improve traffic monitoring and processing capabilities. The resource requirements to support network security appliances are constantly increasing, making efficiency of these systems an essential aspect. The move toward Software-Defined Networking and programmable data planes offers a mean to offload traffic processing functionalities to within the network itself. To this end, we present the 4MIDable framework: a platform that facilitates the integration of existing middleboxes and monitoring appliances with an SDN (P4) network infrastructure. We also present P4Protect, a 4MIDable agent that protects the network from control plane DoS attacks with negligible impact on control plane latency, and P4ID (P4-Enhanced Intrusion Detection), a 4MIDable agent that offers stateful processing and feedback to unmodified Intrusion Detection System middleboxes and reduces traffic processing by over 80% without affecting threat detection rates.