Abstract. Today, information is the most valuable resource. Its possession by the third parties, as well as destruction, may lead to irreversible losses both for any business and for individuals. Accordingly, it is important to protect information systems at all stages of their use. The content of this paper will be useful both to specialists in the field of information security and to ordinary users. The paper focuses on all the main existing ways to penetrate information systems. The paper will allow creating a personal security check sheet.