At present, the security of information systems plays a key role not only for large enterprises, but also for individuals. The information presented in the paper considers an innovative approach to the organization of multi-stage protection of information networks based on access matrices created and specified by data on the degree of criticality of protected files against illegal actions of third parties. The authors proposed to use several levels of criticality with three degrees: critical for program running; important for programs; not critical to programs. Besides, an algorithm for determining the criticality level by file extension as universal is proposed as the basic one. Timely response to changes in critical files not only of the operating system, but also of all programs significantly increases the security of enterprise systems. Moreover, the proposed method can be used to minimize the loss of important data.