One of the most recent hacks in the digital currency space, the attack on South Korea's Bithumb exchange, saw thieves nab $30 million in stolen digital tokens. This was one of the largest thefts of its kind this year, but it is far from the only one.

Indeed, even as cryptocurrencies have proliferated widely and as security systems designed to protect customers and exchanges have grown more sophisticated, hacks and instances of theft have also continued to take place. When the attack involves a service as large as Bithumb, South Korea's biggest cryptocurrency exchange, it shows that even the largest players in the digital currency world are not necessarily safe. Below, we'll explore some of the largest cryptocurrency hacks so far this year.

Bithumb: $30 Million

Bithumb's hack took place on June 19, with about $30 million in tokens stolen, according to Coin Telegraph. Although the exchange has promised that customers will see no impact on their wallets, as it has pledged to repay any lost coins, Bithumb has not come out unscathed. Indeed, although Bithumb was formerly the sixth-largest exchange around the world based on trade volumes but has since plunged to 10th place. The attack focused on Bithumb's hot wallet, a storage mechanism less secure than a cold wallet system.

Coinrail: $37.2 Million

Before Bithumb, there was Coinrail. The rival South Korean exchange was hacked just over a week before Bithumb. Thieves took about $37.2 million worth of digital currency, with the bulk of tokens stolen including those of Pundi X and Aston coins. Bitcoin lost around 11% of its total value in the immediate aftermath of the hack, although it remains unclear to what degree the Coinrail hack had an impact on this fluctuation. The exchange is shut down for the time being in order to repair damage done by the breach; it plans to reopen sometime this month.

BitGrail: $195 Million

Italian exchange BitGrail was hacked in early February, with team members suggesting that $195 million in the token nano was stolen. At this point, though, Coin Telegraph suggests that there remains confusion about the hack itself; the blame may rest with BitGrail founder Francesco Firano, the nano development team or hackers.

Coincheck: $534 Million

In January, the Japanese exchange Coincheck suffered an attack which cost it 523 million NEM coins valued at about $534 million. Again, a hot wallet was the culprit in the theft. The Coincheck hack was larger even than the notorious Mt. Gox hack; NEM Foundation president Lon Wong described it as "the biggest theft in the history of the world." Nonetheless, Coincheck survived the hack and continues to operate, although it was bought in April by a traditional Japanese financial services company called Monex Group.

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