Bithumb said that the thieves stole a database of user information off the personal computer of an employee, rather than off the company's internal network. The attackers allegedly nabbed the names, email addresses, and mobile phone numbers (no passwords, apparently), of more than 31,800 customers, according to a Monday report from Yonhap, a South Korean news wire.
After discovering the breach, which affects roughly 3% of the site's customers, Bithumb reported it to South Korean authorities on June 30, Yonhap said. The robbers have been targeting customers' accounts in an effort to drain their digital currency wallets. The hackers have allegedly made off with hundreds of millions of South Korean won, or tens of thousands of dollars worth of cryptocurrency, according to local media reports.
Bithumb said its corporate network had not been compromised and that the reason for the wallet thefts had to do with phishing attacks.
"The employee PC, not the head office server, was hacked. Personal information such as mobile phone and email address of some users were leaked. However, some customers were found to have been stolen from because of the disposable password used in electronic financial transactions," the exchange said in statement, per a translation provided by Brave New Coin, a website that tracks digital currencies.
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Since the end of June Bithumb customers have been complaining about attacks in posts on Naver.cafe, a South Korean social media site. One person reported to have lost 1.2 billion won, although the Fortune was unable to be verify the claim.
Bithumb said in a Monday notice that it would reimburse victims of the data leak 100,000 won, or about $87, per person. The exchange said it would also compensate people for additional losses related to the attacks.
"For those who have suffered additional damage due to this incident, as soon as the amount of damages is confirmed, we will reimburse the entire amount of damages," Bithumb said in a note, rendered in English via Google Translate.
Bithumb did not immediately respond to Fortune's request for additional information.
Bithumb is South Korea's top crypto exchange, and a leader globally for trading Ether, the cryptocurrency associated with the Ethereum computing network. The exchange rose to the number one spot globally in the days after due to increased trading activity
As the cryptocurrency sector booms, attackers are setting their sights on people's digital currency wallets. Two months ago hackers pilfered Yapizon, another South Korean crypto exchange, to the tune of 3,816.20 Bitcoin, or more than $5.5 million. Attackers have also been targeting Coinbase, one of the largest and most well-known cryptocurrency brokerages in the United States.