აბსტრაქტი. Each manager (manager) of a critical information infrastructure facility is interested in the answer to the question of how to evaluate the effectiveness of the information security and cybersecurity system. The relevance of the research topic is due to the lack of indicators and mathematical criteria for evaluating the effectiveness of the functioning of critical information infrastructure facilities. The main aspects of the work. For an unambiguous answer to the question of how and how to evaluate the effectiveness of the functioning of the information security and cybersecurity system, the article considers the indicators and mathematical criteria of effectiveness. Scientific novelty. The scientific novelty of the obtained result lies in the fact that indicators are proposed and mathematical criteria for possible evaluation of the effectiveness of the information security system and cybersecurity of critical information infrastructure objects are determined.