First off the engine core... is it DirectX, Vuclan, or OpenGL. All those graphics APIs use different libraries and different ways of rendering graphics, even different languages, like OpenGL it is cross platform it is available on most top languages like Java, C#, and C++. Like in OpenGL games you don't know which OpenGL version, or language devs use on their game so if fortnite uses OpenGL API with c# language so if I come with DLL (Like current one made with C++ and Assembly) and tried to inject it, it won't even run it because it is running the game in different language, in different APIs, and different runtime enviroment hence not all games cheating uses injections, because some games injection is incompatible like Dota 2. When an injection happens it is basically injecting code to the memory of the game while it is running, so basically game thinking this page of code is part of me so i'll just run it. If you want to learn more about Anti-cheats look at rainbow six anti-cheat (BattleEye) it is multipurpose, not only it is anti-injection, even stealth injection, it is made with machine learning so it actually can read your inputs and how you play to determine if you are cheating. I can't just make anti-cheat without knowing the run time of the game and how it runs. It is impossible.