(SEOUL) — A leading South Korean cryptocurrency exchange said Wednesday that $31 million worth of virtual currencies have been stolen by hackers, a latest in the series of recent hacks that raised security concerns. Bithumb, South Korea’s second-largest exchange, said cyberattacks from late Tuesday night to Wednesday morning led to the loss of 35 billion won worth of cryptocurrencies. Bithumb said it has suspended trading and exchanging cryptocurrencies to Korean won following the hacking. It did not say which types of coins were lost.