We address the dependence of critical infrastructures-including electric power, telecommunications, finance and transportation-on vulnerable information systems. Our approach is based on the notion of control systems. We envision hierarchical, adaptive, multiple model, discrete-state distributed control systems to monitor infrastructure information systems and respond to disruptions (e.g., security attacks) by changing operating modes and design configurations to minimize loss of utility. To explore and evaluate our approach, we have developed a toolkit for building distributed dynamic models of infrastructure information systems. We used this toolkit to build a model of a simple subset of the United States payment system and a control system for this model information system.