The book attempts to respond to objective needs for the formation of conceptual and methodological foundations for ensuring information security in the development of the information society. It sets out the foundations of the theory of information protection, combining a wide range of problems related to ensuring information security in the process of generating, processing, storing and transmitting information in automated systems and at objects of informatization. Various approaches to modeling information protection systems and processes in conditions of incomplete and unreliable source data are analyzed. Particular attention is paid to the heuristic component of the process of finding the most rational solutions in various information protection situations. For specialists in the field of information security, it will be useful for students and graduate students of higher educational institutions, students of continuing education courses.