There is currently no shortage of information security (IS) literature. However, most books on this topic provide only a small part of the information that is necessary for integrated information security in the enterprise. For example, some security textbooks focus on security regulations, but very little is said about the technical implementation of threats and protection against them. On the other hand, there are many books devoted only to technical aspects (the so-called “hacker eyes” view). These books describe in detail the implementation of specific protections, but it is not always clear in what practical situations it can be useful. This book is an attempt to overcome the one-sided approach to the topic of IS. The book is intended for system administrators and users of small and medium-sized networks engaged in the protection of corporate resources. Here are both technical information describing attacks and protection against them, as well as recommendations for ensuring information security with relevant examples.