I saw different levels of cheating. Lv 1 is time limit losses when I am about to win or make a play that decimates. I have read this may be people logging into a 2nd device and it somehow trips a time limit loss. Lv 1 hacks , to my knowledge, have no evidence.
Lv 2 hacks are obvious and can be seen live streaming on Youtube...these are hacks that the person is likely using some preloaded environment on their computer to work exploits in the game...like showing them all of your cards in the hand and the top of your deck and your traps...they can see it all the whole duel. They exploit effects that already exist like showing the hand and parasite.
Lv 3 hacks are wild...and they would have to be proxying the connection and changing data or something. These can be seen when: a non equip or non continuous spell stays on the field, your monsters cannot attack though no effect exists to cause that condition, a time limit loss for you on your opponents turn. These are the most rare and in some cases I think it may even be people at Konami.
I would call that a lv1 hack. That is the one that has no discernible evidence except that it happens...and still has the possibility of not actually being a hack. But the timing is usually so spot on that it seems less probable to be a glitch. This is maybe the most commonly occurring hack.
Kreature
Massiv