Abstract: Described herein is a system and method for improving cyber resilience for determining an optimal security policy for a network. The system uses an objective function to balance cyberattack risks, accessibility to network resources, resource limitations, minimum mission availability requirements within a network environment, or a combination thereof. The objective function comprises objectives (one or more variables that enhance accessibility to network resources and reduce cyberattack risks) and constraints (one or more variables that characterize resource limitations or minimum mission availability requirements within a network environment). The optimal security policy is selected by solving one or more optimization problems. The optimization problem may be solved by determining candidate security policies that meet the constraints and selecting among candidate security policies having the highest score for a given objective function.