In a brazen attack on the popular video game Axie Infinity, hackers swiped $625 million in cryptocurrency, marking one of the largest crypto-thefts to date amid rising rates of such crime. The theft occurred last Wednesday, when hackers infiltrated Ronin, the underlying blockchain that powers the game. Developers at Sky Mavis, which runs Axie Infinity and Ronin, said they discovered the breach only Tuesday, the Washington Post reports. Axie Infinity uses a “play-to-earn” system that combines finance and gaming, powered by NFTs, unique tokens that can be traced back to a user. Players buy creature-centric NFTs to gain entry into the game, and then spend more crypto to acquire and breed various beasts they can deploy in battles. The NFTs have both in-universe and real-world value, adding digital-money buzz to traditional gameplay. The blockchain is the public record of where cryptocurrency transactions take place, functioning as a financial nerve center. The Ronin hackers made off with some 174,000 ETH, the currency associated with the Ethereum blockchain, and nearly 26 million in USDC; collectively the two are worth abut $625 million. USDC is a stablecoin, which means its value is pegged to the U.S. dollar. Crypto hacks are becoming more common as trading activity increases. A hack of the Bitmart platform in December resulted in a theft of nearly $200 million in currency. Last summer a hacker hit Poly Network, which allows blockchains to work together, for a number exceeding $600 million, though eventually returned the money. Trading in Axie Infinity was frozen Tuesday as fans and experts questioned whether the hack might make companies and players more skeptical of play-to-earn games. It remains to be seen how much of Ronin’s hacked cryptocurrency will make it into general circulation. The conversion into traditional, or fiat, currency is considered one of the major hurdles for would-be crypto thieves, who struggle to get real-world dollars without catching the eye of investigators. Such realities could deter hackers, as they realize stealing the money is only half of the battle.