Australian slot machine manufacturer Aristocrat confirmed that a Russian hacker who claimed to be able to turn casino machines into virtual ATMs tried to extort the company.

The St. Petersburg-based hacker, who went by the name Alex, told tech magazine Wired in a lengthy interview that he made millions of dollars through a venture built on his talent for reverse engineering the pseudorandom number generators (PRNGs), which govern how slot machine games behave.

Alex, who described himself as a mathematician and programmer, has “a legion of field agents” visiting casinos in different countries around the world to record video of the machines on their phones. Four of these agents were convicted of fraud charges in the United States several years ago.

Back in Russia, Alex and the rest of the team would analyze the video to determine when the machine’s odds would favor a payout. Then, they send “timing data” through a custom app on the agent’s phone—a strategy that could earn the team more than $250,000 weekly.