Ah, thanks for actually explaining rather than saying "there is no cheat system" then going on about how this and that was secure then hackers broke in, etc. Some of us have no idea how these things work.
With that, I agree: MK8 has no cheat system.
So I will give you a simple example of how anti-cheat system would work.
Say you have a player with X,Y,Z coordinates in 3d space. As these coordinates change, the player moves across the screen right?
Well, a cheater could modify these values in RAM to give him/herself super speed or teleport to a coordinate.
A real "anti-cheat" system would take a sample of these values across a range of time and say "Hey, this player's sample velocity is higher than the maximum velocity allowed by the game engine. I'm going to start looking at him to see if he does it again".
Same idea goes for infinite power ups etc.
There are also functions used to introspect RAM to see if protected areas are being modified. As well as functions to see if firmware has been tampered with. For example CoD:Ghosts for PS3 does this, although you can patch these functions return values to bypass them.
It is a constant battle of developers to use security through obscurity to make it too difficult and time consuming for malicious players to keep up with the latest integrity checks.
I don't want to see public online play ruined. It is not funny to have lulz at others expense. People come and play games to relax, to get away from the stress in their lives and to enjoy the game with their friends and family. It takes a special kind of sick psychopath to ruin online games for other players.