No worries , but i think I’m not being clear if you build it from scratch. how are you going you going to compile it ?

Your welcome but that’s the point he was making even if you build everything on your own. The backdoor would be in the compiler. So even if you built /bin/login for example he would just inject it at compile time when compiling your code. But then you asked I will just compile the compiler but you have to compile it at some point and he can inject the code back into the compiler at that point.

If you read this you will never trust anything again. If you aee not familiar with him that is Ken Thompson one of the father’s of Unix.