OpenFlow is an open standard that has gained tremendous interest in the last few years within the network community. It is an embodiment of the software-defined networking paradigm, in which higher-level flow routing decisions are derived from a control layer that, unlike classic network switch implementations, is separated from the data handling layer. The central attraction to this paradigm is that by decoupling the control logic from the closed and proprietary implementations of traditional network switch infrastructure, researchers can more easily design and distribute innovative flow handling and network control algorithms. Indeed, we also believe that OpenFlow can, in time, prove to be one of the more impactful technologies to drive a variety of innovations in network security. Open-Flow could offer a dramatic simplification to the way we design and integrate complex network security applications into large networks. However, to date there remains a stark paucity of compelling OpenFlow security applications. In this paper, we introduce FRESCO, an OpenFlow security application development framework designed to facilitate the rapid design, and modular composition of OF-enabled detection and mitigation modules. FRESCO, which is itself an OpenFlow application, offers a Click-inspired  programming framework that enables security researchers to implement, share, and compose together, many different security detection and mitigation modules. We demonstrate the utility of FRESCO through the implementation of several well-known security defenses as OpenFlow security services, and use them to examine various performance and efficiency aspects of our proposed framework.