Crazydude5, most the time a bypass is done through modification of the game code in question. The most common but more detected techniques are "hooks" which is where you redirect a function to your own custom code and then redirect it back. Most the time this is done through a combination of a .exe file which is the "Loader" and the .dll file which is injected into the program as a module. Of course theres much more involved and complicated ways to go about this to bypass obvious detection methods but its not the easiest thing to do unless you have real motive to do it yourself. Honestly I've messed with both hacking packets to be sent via memory and "hooks", both work reletavely well but again you either have to keep it private or be willing to recode the way it works 1-2 times a week lol. I avoided public releases of my experiments for that very reason.
*NOTE* I would like to add that cheat engines get detected because they use a set few of methods to access the memory of other programs so either you have to find a way to hide that method from being detected or you have to recode the memory accessing method to use a different route / method. I have never had luck with getting a public cheat engine to be undetected the closest one I found was "Memory Hacking Software" which would allow you to randomize the filename, md5 hash, and many other things such as process name, window title, etc. It was great at avoiding many commonly used methods of detection.