For the second time in a year, South Korean cryptocurrency exchange Bithumb has been hacked, and this time around, hackers stole the equivalent of 35 billion won ($31.6 million) worth of cryptocurrency.
The attack took place on the night between June 19 and June 20, according to a statement on the company's website.
Bithumb did not reveal any details about this latest hack, such as what cryptocurrency the hackers stole, how they got into their IT system, or how they exfiltrated funds.
Some users reported on cryptocurrency-focused forums that they were missing Ripple (RPX) from their accounts, but this information was never confirmed by the exchange.
In the aftermath of the hack, the company immediately blocked user withdrawals to prevent the hacker from stealing more funds.
Bithumb then moved to relocate most of its funds to a cold (offline) wallet for safe-keeping, until it audits, rebuilds, and roots out the hackers from its IT system.
The company is now warning users to not deposit new funds into their accounts or attempt to make payments, as the transactions could be lost during the system migration.
[Notice for the temporary suspension of the deposits]— Bithumb (@BithumbOfficial) June 20, 2018
Due to the increasing safety issues, we are changing our wallet system.
Please do not deposit until we notify.
*All deposits are not deposited into your wallet until all changes are completed.
*All deposit and withdrawal service will be stopped to make sure the security. We will keep notice you of the restart of the service. We apologize for your inconvenience and thanks for your understanding.— Bithumb (@BithumbOfficial) June 20, 2018
The company said it was planning to use its reserve funds to compensate all users who lost currency in the recent hack.
Bithumb suffered a similar hack in July 2017, when an unknown hacker stole an unknown sum of Bitcoin and Ether from the exchange.
Today's hack continues a year-long trend of South Korean cryptocurrency exchanges suffering hacks. Past victims include Coinrail ($40 million), YouBit (hacked twice, has shut down) and Yapizon ($5.5 million). Several cyber-security firms have stated that North Korean state hackers have been behind some of this hacks, albeit not all.
Bithumb was considered one of the top 10 most popular cryptocurrency exchanges on the market before today's hack. Bitcoin price fell 3 percent following Bithumb's announcement.