The hack of roughly $66 million worth of bitcoins from the Hong Kong-based Bitfinex exchange focuses on poor security practices and weaknesses in bitcoin exchanges. Accordingly, this makes the hack one of the biggest bitcoin thefts to date, but is relatively small in comparison with the loss of more than $450 million worth of bitcoins by the Tokyo-based Mt. Gox bitcoin exchange in 2014.
A statement on Bitfinex's website says "We are investigating the breach to determine what happened, but we know that some of our users have had their bitcoins stolen. We are undertaking a review to determine which users have been affected by the breach. While we conduct this initial investigation and secure our environment, bitfinex.com will be taken down and the maintenance page will be left up." Security breaches of this type have raised questions about the viability of Bitcoin. Bitfinex said the theft had been reported to law enforcement.