Binance said hackers were able to withdraw 7,000 Bitcoin (£30.9m) in one transaction after using “a variety of techniques, including phishing, viruses and other attacks”.
The Japan-based exchange’s chief executive Changpeng Zhao, known as CZ, said the transaction represented “about 2%” of Binance’s total Bitcoin holdings.
CZ said Binance will use its secure asset fund “to cover this incident in full” and a “thorough security review” will be carried out.
Binance warned its account holders that it expected the review to take around a week, during which time withdrawals and deposits will remain suspended, although trading would continue to be possible.
“Not the best of days, but we will stay transparent,” he tweeted.
The theft only affected the exchange’s “hot wallet”, which refers to a cache of Bitcoin connected to the internet.
“The hackers had the patience to wait, and execute well-orchestrated actions through multiple seemingly independent accounts at the most opportune time,” CZ said in a message posted online.
“The transaction (was) structured in a way that passed our existing security checks.
“It was unfortunate that we were not able to block this withdrawal before it was executed.
“Once executed, the withdrawal triggered various alarms in our system. We stopped all withdrawals immediately after that.”