Digital currencies like Bitcoin are very hot right now, and hackers are apparently looking to take advantage of that, as one of the largest Bitcoin exchanges in the world was just hacked.

Bitcoin and other cryptocurrencies surged in the past few months, which explains why people with malicious intentions would be looking to steal this precious virtual coin.

According to Yonhap News, hackers hit Bithumb, compromising 30,000 accounts. That represents 3% of the exchange’s customers. It’s unclear how much money, if any, was stolen, but some people said they lost money in the attack.

Bithumb realized last week that one of its employees’ home personal computers was hacked. That’s how the hackers may have stolen customer data. But that data does not include passwords, and the company said that digital wallets that contain Bitcoin and other coins were not emptied.

On any given day, Bithumb is the world’s third or fourth exchanges in the world by cryptocurrency trade volume, Business Insider explains.

A BraveNewCoin report says that Bithumb owns more than 75% of the South Korean Bitcoin market volume, and the exchange hosts 10% of the global Bitcoin trade. The same story notes that some 100 customers may have lost hundreds of millions of won, with one person having lost 1.2 billion won after the hack. To put things in perspective, 1 billion won is the equivalent of $870,000. Or nearly 340 Bitcoin at current prices — 1 Bitcoin costs $2,561.14 as of this moment.

Affected customers have already filed a complaint with the National Police Agency’s cybercrime report center.