It was a good learning experience on B.O.F (buffer overflow), the most basic of system hacking. Thanks to this, I gained confidence in system hacking and I wanted to challenge other system hacking war games or CTF problems. However, since the difficulty level is set to 'beginner' instead of 'introductory', it may be unfamiliar to someone who suddenly hears it without any knowledge, so it would be good to take the lecture after acquiring the following prerequisite knowledge. 1. Hexadecimal number display method (Hexadecimal number notation: 0,1,2,3 .... 9, a, b, c, d, e, f) Ex.) You should be able to understand that 0x88 + 0x08 = 0x90 when calculating in hexadecimal. 88+8 = 96 is the calculation method in decimal, and you need to understand that in hexadecimal, 0x88 + 0x08 = 0x90. 2. When explaining gdb and stack structure, etc., some register-related content You don't need to know the roles of each register in detail, but you just need to know that there are such registers. And it would be better to know how input values and data are stacked in the stack structure. 1) [Good video reference related to stack memory] (Video title: System Hacking Lecture 5 - Understanding Memory Structure (System Hacking Tutorial 2017 #5)) URL: https://www.youtube.com/watch?v=TxWOaKE5w_s --> Rather than completely understanding the entire content, it would be good to just understand that stack memory works this way. 2) [Reference materials related to gdb and registers] -> I have gdb at home... Do you want to see the memory? (1) URL: https://bpsecblog.wordpress.com/2016/03/08/gdb_memory_1/ -> I have gdb at home... Do you want to see the memory? (2) Summary data URL: https://haerinn.tistory.com/85 --> This summary data is especially closely related to the core of the solution to this lecture. I think it would be good to study in advance in the order I indicated the URL. Lastly, I would like to thank juntheworld for uploading a great lecture. Thanks to you, I was able to take a good step toward hacking the system. Thank you.