Some years ago there was a controversy about how a group of Chinese got the jackpot of a kind of slot machine that had a bug in its software. They approached to it with the mobile phone and few minutes later the machine started to vomit coins. But experts in the subject didn’t find any relation mobile phone and machine.
So after more investigations, police knew that a lot of them used the ear to get the jackpot. Depending on the sound of a coin dropping within the machine the Chinese knew that would have jackpot soon or not. If the sound of the coin into the box was hollow it meant that the machine was wide. If the sound was hard it meant that the machine was full of money, so more possibility to get the big prize.
Nowadays, to cheat is easier for people that know how to proceed. Finding sites where teach you how hacking a casino online is the best manner to practice. Although you know, it is illegal, and only the real gangsters are able to get money cheating, but they always finish their life in the jail, one day or another.