Coincheck said it was investigating "unauthorised access" of the exchange that appeared to result in a loss worth half a billion US dollars of NEM, the 10th biggest cryptocurrency by market capitalisation. "At 3 am (1800 GMT) today, 523 million NEMs were sent from the NEM address of Coincheck. It's worth 58 billion yen based on the calculation at the the rate when detected," said Coincheck's chief operating officer Yusuke Otsuka.
Coincheck said in a statement it would repay the roughly 260,000 owners of NEM coins in Japanese yen, though it was still working on timing and method. The theft once again puts spotlight on security and regulatory concerns about bitcoin and other virtual currencies even as a global boom in them shows little signs of fading.
Citing sources, Reuters reported that Japan's Financial Services Agency (FSA) sent a notice to the country's roughly 30 firms that operate virtual currency exchanges to warn of further possible cyber-attacks, urging them to step up security. The financial watchdog is also considering administrative punishment for Coincheck under the financial settlements law, one of the sources said.
After the exchange suspended deposits and withdrawals, NEM plunged more than 16 percent in a 24-hour period, according to CoinMarketCap.com. Japan is the first country to license crypto exchanges, with its first 11 licenses handed out in September.