For centuries, the state has been improving the system of surveillance over its citizens, while at the same time building a rigid barrier that was supposed to prevent the penetration of enemy emissaries. A special and completely autonomous organization is intelligence. And here it was necessary not only to train future eyes and ears “outside”, but to develop the principle of their introduction into the enemy’s camp. The author examines the activities of special bodies in virtually all countries of the world. The principle of operation is approximately the same, but the difference is always noticeable: national characteristics, longevity (or, conversely, “tender age”) of a particular intelligence service distinguish it from others. If you are interested in the work of state security agencies, read this book.