I am a 4th year computer science student. In the case of Spring Security, if you search on Google, you will find a lot of information, and it is also a good idea to refer to the official reference on spring.io. However, in the case of security, the process of reorganizing scattered information is very difficult. Even if you search on Google without knowing anything, it only tells you how to set up SecurityConfig, and it does not explain in detail why it is used, so if you apply it to a personal project, you will encounter numerous errors. In my subjective opinion, if you do not know anything about security, I am sure that purchasing this lecture is much cheaper than the cost of searching and finding it yourself. If you are taking the lecture, it seems better to skip Chapters 1 and 2 at first and go straight to the practical training. If you are doing the practical training and you get stuck for some reason, you can understand it better and internalize it faster by looking at the detailed API explanation in Chapters 1 and 2. For example, when I only heard about Authentication Flow in theory, it was quite difficult, but when I applied it to my project in Chapter 3 of the practical training and listened to it again, the flow chart caught my eye right away. The PPT is also well organized by each step, so it is a material that I can carry with me for the rest of my life. I unconditionally recommend it to those who, like me, have simply sent password values directly to the DB without encryption in past projects, or made it so that all members who sign up can delete posts written by others, or simply made projects as a patchwork.