| Updated: September 26, 2025Slots are the most popular casino games, generating up to 70% of casino operators’ revenue worldwide. Slot machines have been around for more than a century and have undergone many changes since they first appeared. The invention of the microchip completely changed how slots are played and how they pay out.
The early machines were purely mechanical and relied on physical strips of symbols called reels. After a player inserted coins into the slot and pulled the lever, the reels spun. Because space on the physical reels was limited, these mechanical machines featured fewer symbols.
Modern slots use virtual reels with unlimited space. This design allows for more symbols, which in turn increases the number of possible combinations and enables developers to experiment with different odds, volatility, and payback percentages. The outcomes of spins are determined by microchips that use random number generators to produce fair results.
Pseudo vs. True Random Number Generators
There are two types of Random Number Generators but those used in most modern slots (and online casino games in general) are pseudo RNGs. The unique thing about the pseudo RNG is that it creates an output, i.e. an outcome, without using external data. It relies solely on a complex algorithm, a set of predetermined constants, and a seed. The seed number is of extreme importance here because it defines the starting point when the RNG generates a string of random numbers.
True Random Number Generators (also known as Hardware Random Number Generators) are capable of producing results that are indeed unpredictable. This type of RNG does not rely on seed values because the results it yields are never derived from repeatable algorithms.
Seed numbers are necessary in this case because computer programs are incapable of generating truly random numbers. They rely on a set of specific rules, i.e. algorithms, to mimic randomness. As complex as these algorithms are, they still follow a pattern. Thus, a sequence of random numbers can be reproduced if one knows the initial seed value.
Rather, it derives random numbers from digitized images of naturally occurring phenomena, such as atmospheric and thermal noise or the decay of radioactive elements. Any source of natural entropy will do.
The pseudo RNG uses mathematics but there is nothing random about mathematic calculations. A given input would inevitably produce the same output. Moreover, the random number sequence is bound to repeat itself after a certain number of trials, which makes it easier for gaming auditors to inspect the slots for fairness.
One of the main reasons why true RNGs are superior to their pseudo counterparts is that the former are insusceptible to hacking. Since no repeatable algorithms are involved here, a hacker would be unable to predict future numbers even if they manage to figure out one number.
This is not to say that a slot player can discern this pattern and deduce when it is about to repeat. The RNG spews seeds every millisecond. It normally takes one or two numbers it has generated last and uses them as part of a mathematical operation to produce a new random result.
With that in mind, true RNGs are more costly from the casinos' perspective. Like all material objects, hardware components are subject to entropy. They tend to wear and tear over time and therefore are more expensive to maintain.
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Can You Beat the Random Number Generator in Slots?
Another frequently asked question is whether players can beat a slot’s Random Number Generator. The short answer is that this is technically possible, although very few people have ever managed it.
As we previously explained, some slots use pseudo-Random Number Generators that rely on mathematical algorithms to produce unpredictable outcomes. This can leave them vulnerable to skilled hackers, but only someone with exceptional programming expertise is likely to succeed.
Nevada Regulator's Employee Reprograms the RNG Russian Hackers Unpuzzle Secret of the RNGNevada Regulator's Employee Reprograms the RNG
There are two well-known cases of people beating a slot’s RNG. The first involved a programmer named Ronald Harris, who worked for the Nevada Gaming Control Board and exploited his position in the early 1990s.
Harris was tasked with analyzing the software of slot machines across Las Vegas casinos for flaws. Being an expert in his field, he quickly realized that the machines could be tampered with to generate consistent winnings.
As an employee of the local regulator, Harris had access to the confidential code used to program the slots’ RNGs. He reprogrammed certain machines so they would pay out specific amounts of money when coins were inserted in a particular order. One sequence required 3 coins on the first spin, 2 coins on the second and third spins, 1 coin on the fourth spin, 6 coins on the fifth spin, and finally 5 coins on the sixth spin.
This sequence ensured substantial wins. The only problem was that Harris was prohibited from gambling because he worked for the Nevada regulator. To get around this, he enlisted a close friend who had recently lost his job.
The friend, Reid McNeal, simply inserted coins into designated machines in the exact order Harris had specified. The pair split the profits evenly. Their scheme proved so successful that they shifted their operations to Atlantic City to avoid detection.
They were winning respectable sums, but greed eventually caught up with them. In 1995, Harris decided to branch out from slots to keno machines. Managers at Atlantic City’s Bally Park Place Hotel and Casino grew suspicious after his partner won $100,000 at keno from a stake of just $100.
The scam earned Harris a seven-year prison sentence, although he was released after only two years for good behavior. He was also added to the black book of the Nevada Gaming Control Board, permanently banning him from entering any Nevada casino.
Russian Hackers Unpuzzle Secret of the RNG
In June 2014, the accountants at St. Louis’ Lumière Place Casino noticed that several of their slot machines were behaving strangely. Over just two days, the machines had paid out far more money than expected, even though no large jackpots had been hit.
Because the machines relied on a complex, predetermined code that does not change from day to day, the most plausible explanation was that someone had cheated.
After carefully reviewing surveillance footage, casino management spotted a man whose behavior seemed odd, although he did not match the typical profile of a slot cheat. The man was 37-year-old Russian Murat Bliev, who was part of a larger group of scammers.
Bliev would hold his mobile phone close to a machine’s screen and then stand up as if he were leaving. A few minutes later he would return to give the machine one last spin – a move that almost always paid off. In just two days, he managed to extract about $21,000 from the casino.
An extensive investigation by the Missouri Gaming Commission revealed that other casinos had been cheated in the same way by different members of the crew, which operated in the United States, Europe, and Macau.
Bliev and one of his associates were eventually detained and confessed to the scheme. After Russia outlawed gambling in 2008, many Russian casinos sold their gaming equipment to anyone willing to buy it. That is how slot machines manufactured by Aristocrat ended up in the hands of the hacker group for which Bliev worked.
The hackers examined the machines and successfully reverse-engineered their Random Number Generators. This knowledge of the machines’ code enabled them to identify outcome patterns and exploit them.
The operation worked like this: associates would scan casino floors for specific machines, record several dozen spins, and upload the data to the crew in Saint Petersburg.
The team analyzed the results to spot current spin patterns and determine the exact moment when the odds shifted in favor of the player. They then sent timing markers to their partners’ phones via a custom mobile app. The device would vibrate a split second before the player needed to press the button for a winning spin.
Although the method was not 100% effective, it still allowed the scammers to secure unusually high payouts. To avoid detection, each associate would take only about $1,000 from any one machine, yet a team of four still managed to earn weekly profits of around $250,000.