“When hackers penetrated a secure authentication system at a bitcoin exchange called Bitfinex earlier this month, they stole about $70 million worth of the virtual currency. The cyber theft — the second largest by an exchange since hackers took roughly $350 million in bitcoins at Tokyo’s MtGox exchange in early 2014 — is hardly a rare occurrence in the emerging world of crypto-currencies.”

Source: Cyber threat grows for bitcoin exchanges | Reuters