Information technologies are penetrating deeper and deeper into our lives. Not to mention the companies directly involved in the development or implementation of IT; banks, large trading companies, hospitals, museums can no longer do without them... And this list is easy to continue. And increasingly, information systems and networks and the information stored in them are becoming the target of robbers, terrorists or simply vandals. How can you make sure your information is secure? That an attacker or just a frolicking teenager, having stolen or destroyed data on your network, will not destroy both your personal destiny and the destiny of the entire company? The book you are holding in your hands is dedicated to these questions. Unfortunately, technical security problems are not always obvious to those who make decisions about allocating funds and carrying out the necessary activities. But in the book you will not find the technical details necessary for system administrators and security specialists. The author examines specific, fairly typical situations that she encountered as a security auditor, and provides simple advice on how to make sure that this is impossible in your company. The book will give a lot of useful advice for top-level managers and specialists responsible for information security of companies.