Coinrail did not specify the value of the currency that was taken in the attack at the weekend but said it was working with authorities and other coin developers to track down the culprits.
The firm, which trades more than 50 cryptocurrencies, added that it had frozen all exposed coins -- Fundus X, Aston, and Enper -- and other units had been taken offline in a "cold wallet".
"The markets are so thinly traded, primarily by retail accounts, that these guys can get really scared out of positions," he said. "It actually doesn't take a lot of money to move the market significantly."
Cryptocurrencies have plunged since the end of 2017, when bitcoin hit a record high near USD 20,000, having surged from less than USD1,000 just 11 months earlier. The unit is now worth around USD 6,780.
South Korea is one of the biggest markets for trading in digital currencies but the boom in their popularity has forced the government to tighten regulations, following similar moves in other countries.
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