Slot machines, aka fruit machines and one-armed bandits, have been getting a little press in the news amongst the geek community lately. A recent case of a slot machine with faulty software has raised the question of whether a person playing a machine is guilty of a crime if they knowingly exploit a defect.

Doubly, there is a recent report by a Stanford student on the psychology and design of slot machines. A good exercise for the budding hacker is to reverse-engineer a slot or other casino game on their home computer, using whatever programming language they’re handy with. It’s good exercise both for programming and figuring math probability - one of the weakest areas the public has in math. And of course, it will help teach you how slots work.

A little-known fact is that slot machines can be hacked in much the same way that regular computers can be hacked - and one famous guy actually did it! That would be one Ronald Dale Harris, whom you might call the Kevin Mitnick of slot machines. There’s been a few documentaries about his story running around on cable TV.

Harris worked for the Nevada Gaming Control Board in the early 1990s. It was his job to find flaws in the software that runs computerized casino games. What he ended up doing was write the program which casino employees would take around on a portable unit to plug into slot machines and test to make sure the software running on them was correct. Except that he wrote a little exploit and slipped it into the code!

The exploit worked in much the same way as a root-kit for the computer: it installed a patch in the slot machine which would trigger a jackpot payout upon recognition of a certain code. The “code” to trigger the payout would be a sequence of coins - for example, one coin, then two, then three, then one, etc. The exact sequence is not known.

But as a Gaming Commission employee, he was forbidden by law from even playing the games, so he had to hire an accomplice. Together, they collected thousands of dollars, but after a couple years of this, Harris’ reliance on an accomplice would be his downfall.

Harris decided to try playing for bigger stakes, and so he reverse-engineered the random number generator used in Keno games. Using a radio communication, Harris had his friend play Keno on the floor, while he watched the results on TV from his motel room and typed the numbers into a program on his laptop. The program eventually recognized the number sequence and correctly predicted the next draw - since the random numbers were actually pseudo-random numbers generated from a mathematical algorithm. But Harris’ accomplice blew it by fumbling his ID when he went to collect the winnings, showing a fake ID at the counter when he’d used his real ID to check in. The duo was busted!

Harris only served two years in prison for his crimes, and today works in publishing. He is of course barred from ever showing his face in a casino again. As for the clean-up: today’s casinos use a much stronger method of generating random numbers, and the compromised slot games were patched. But will we ever know exactly how many machines were hit, whether every one was accounted for, or what other exploits Harris rigged during his career?

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