South Korean cryptocurrency exchange Bithumb fell victim to an insider attack, which allegedly led to a loss of $19 million in cryptocurrencies.

On 30 March, Bithumb announced a temporary suspension of deposits and withdrawals "in order to provide more stable service." According to the official statement, on 29 March, the monitoring system recorded abnormal withdrawals of funds. The following internal investigation revealed that the abnormal activity was associated with an attack on the trading platform, with some insider agents among the personnel taking part in the hack.

"Our security system was focused on repelling external attacks. There was a lack of sufficient probes for internal staff," the Bithumb statement reads.

The cryptocurrency exchange ensures that, after detecting abnormalities, it blocked the possibility of withdrawals in cryptocurrencies. However, according to reports in social media, the attack resulted in about $19 million in cryptocurrencies stolen. Hackers managed to transfer EOS tokens worth about $12.5 million and Ripple tokens worth about $6.2 million to external addresses, in particular, EOS were moved to the exchanges EXMO, Huobi, Changelly, KuCoin, CoinSwitch.

Bithumb commented on this information, assuring that these funds belong to the exchange and customers' funds were not affected.

Bithumb reports that it cooperated with the South Korean police, KISA and other law enforcement agencies in order to provide fair and thorough investigation of the incident. Bithumb also promised to strengthen internal personnel verification process in order to prevent such insider attacks to happen again.

In June 2018, Bithumb also suffered a hacker attack. The exchange suspended deposits and withdrawals, but it still lost $31 billion in cryptocurrencies. Then, Bithumb found a way to return some part of the stolen funds, reducing the total amount of damage by half.