The increased decentralisation and heterogeneity of critical infrastructure systems pose a threat to the safe and secure operation of critical infrastructures by complicating cybersecurity procedures. The increased frequency and impact of cyberthreats have led to the desire to develop coherent security policies. In order to explore the effects of such policies, an ecosystem-level framework for cyberincidents in critical infrastructure systems has been developed. This framework can be used to explore the effects of conceptual defensive strategy designs. The aggregation of these concepts was operationalised around a central degree of critical infrastructure operability. A practical application of the framework is provided in the form of an agent-based modelling study that is capable of simulating the effects of coherent defensive strategies. The framework by itself is limited to exploratory modelling for the sake of generalisability and requires further specification of concepts based on representative infrastructure scenarios for more advanced analysis and design of tangible security policies.