https://www.vice.com/en_us/article/pajapb/40m-hack-is-expensive-lesson-for-binance-ceo-says

Binance, one of the largest online exchanges for buying and selling cryptocurrencies, lost $40 million to hackers on Tuesday in what its CEO described as a “very expensive lesson."

According to a blog post written by CEO Zhao Changpeng, the hackers used a slew of techniques including phishing and viruses to steal roughly 7,000 bitcoins from Binance’s hot wallet (a digital wallet used to handle day-to-day transactions, rather than store reserves indefinitely) in a single transaction on Tuesday. The stolen bitcoins accounted for 2 percent of Binance’s Bitcoin holdings, the blog stated.