Critical infrastructures are so vital for a country that their destruction or incapacity with war, terrorist attack and natural disasters may have irrecoverable effects on security systems together with other social, economic, and public systems. The protection of these facilities is one of the important problems. This study is one of the facility protection problems to determine which facilities will be protected to ensure the uninterrupted demand of a critical zone. Different attack types and counter defense types, which were ignored in previous studies, were taken into account in this study. Disrupting the supply-demand balance for critical systems with limited resources is also included in the model. This paper presents two new mathematical models for the defense of critical infrastructure systems. The contribution of our models is considering different types of attacks and defense options and disrupting the supply-demand balance. The first model is ReIMF and considers different attack and defense types. The second model is SD - FeR ffcIMF and considers supply-balance disruption. Both models are based on RIMF (r-interdiction median problem with fortification) model in the literature. Due to security reasons, it is not possible to find real data to apply the methodology to a real system in our case, therefore we developed a toy problem to solve the models proposed and discussed the results. R ffcIMF model offers solution for problems with unlimited capacity and model SD - FeIMF offers a solution to problems with limited capacity.