Abstract. As the number of network-based attacks increase, and system administrators become overwhelmed with Intrusion Detection System (IDS) alerts, systems that respond to these attacks are rapidly becoming a key area of research. Current response solutions are either localized to individual hosts, or focus on a refined set of possible attacks or resources, which emulate many features of low level IDS sensors.In this paper, we describe a modular network-based response framework that can incorporate existing response solutions and IDS sensors. This framework combines these components by uniting models that represent: events that affect the state of the system, the detection capabilities of sensors, the response capabilities of response agents, and the conditions that represent system policy. Linking these models provides a foundation for generating responses that can best satisfy policy, given the perceived system state and the capabilities of sensors and response agents.