In 2018, as much as $1.7 billion worth of cryptocurrencies were swindled away from investors through a variety of means. The number one culprit in 2018 was cryptocurrency exchanges. South Korean exchange Bithumb announced that it suffered a security breach and theft to the tune of $19 million. Singapore-based cryptocurrency exchange DragonEx revealed that it too had been hacked in March. Experts suggest that social engineering and the utilization of insiders may be the largest threats to the industry in 2019.
Source: https://thehackernews.com/2019/05/bitcoin-ethereum-hacks.html