This paper studies the essence, challenges, etc. of reverse engineering. It explores how the program works with the help of reverse engineering, what data it uses, where and what it sends, as well as what vulnerabilities it has. Through reverse engineering, it is possible to understand how a program works, what data it uses, where and what it sends, as well as the program's weaknesses and how it reacts in the event of a crash. All this will help to improve the product and defeat competitors. The process of reverse engineering may seem simple; however, it is an illusion. Even experienced reverse engineers can analyze the same program for months. And it is not a fact that it will be possible to completely decrypt it. The paper also highlights the jobs reverse engineering is currently used for, and describes the procedure for using the disassembler, providing examples of the areas where reverse engineering is beneficial. It presents the exact ways in which reverse engineering occurs.