The world trends in increasing of threats of natural and man-made nature, a level of terrorist threats, the number and complexity of cyberattacks have caused the actualization of needs for critical information infrastructure protection and improvement it's informational security and functional safety. A critical information infrastructure is considered as a set of information and telecommunication systems, improper operation of which may lead to the occurrence of an accident of critical infrastructure (energy, transport, etc.), as well as to decrease in quality of its services. The subject of paper’s study is the mechanisms for ensuring the safety (protection) of critical information infrastructures. The purpose of the paper is to substantiate the approach to the development of methodological foundations and technologies for assessing and ensuring the safety (protection) of critical information infrastructures taking into account the state and capabilities of modern information technologies. The methods used are: systems analysis methods, mathematical optimization methods, safety, and risk theory methods. The following results were obtained. The main tasks of the critical infrastructure protection system are formulated. The necessity of using the system of protection of critical information infrastructure as part of the system of protection of critical infrastructure is substantiated. The concept and principles of the methodology for assessing and ensuring the safety (protection) of critical information infrastructures are developed, working hypotheses, methods and models necessary for their implementation are suggested. The way of interaction of the elements of the proposed methodology, tasks and elements of the critical infrastructure protection system is shown. The results obtained are aimed at solving of one fundamental problem such as the existence of a contradiction between the intensive development of critical information infrastructures, negative influences and threats of various nature and the lack of methodological foundations, models, methods and information technologies for assessment and assurance of critical information infrastructure security and safety. The results obtained should be used to create elements of informational and analytical support for the decision maker in solving tasks related to the assessment and security (protection) of critical infrastructure

This study aims to solve the problems of the methodology of holistic and systemic approaches and to establish the form of relations between them. In the general theory of systems between the concepts of "system" and "whole" the relation of primacy is established, namely: the system is recognized as primary, and the concept of "whole" is applied to the formation of properties of the system: emergence and integrativity. For the whole, the regularity of the relationship between the part and whole is established and studied. Besides, it is this pattern is the basis for establishing the characteristics of the system and its elements. In this study, it is proposed to abandon this form of relationship between the system and the whole and move on to the study of the whole as an independent object. In the study of this whole, it is also proposed to abandon the establishment of the form of interaction between the part and the whole and to proceed to the study of the interaction of the parts as a whole. The study of the concept of "organized whole" based on the theory of functional systems, which is considered a natural intellectual system, provided the separation of two parts in an organized whole. Thus, the problem of synthesis of the organized whole is solved. For these two parts, the ways of realization of activity in the form of the decision of the corresponding problems are established. On this basis, the logical principle of mutual relations between the parts of the whole and the results of the realization of their activity in the form of a dialectical triple relation "general" - "special" - "singular, concrete" was determined. It is established that the form of representation of the middle member of this relationship, namely, "special" should be the appropriate sign. The proposed approach investigates the mechanism of interaction (dialectical unity) of two active parts of an organized whole, for which the result of this interaction (zero) is known. The relationship between the system and the organized whole is established in the form of "part" - "whole." The logical sequence of formation of contradictions, axioms, and rules of formation and activity of natural intellectual system which is realized in the given work, is an example of the practical application of a logical method of knowledge of laws.