In the world’s biggest cryptocurrency heist,North Korea is a suspect.

North Korea is no stranger to cryptocurrencies: The rogue regime has been accused of launching a global ransom attack to raise bitcoin, hacking South Korean exchanges, and mining crypto both within its borders and secretly on your computers. Now, it has become a suspect in the world’s largest crypto heist, Reuters has reported.

South Korea's national spy agency told a parliamentary committee on Monday that North Korean hackers may have been behind the theft last month of about $530 million worth of digital tokens from Japanese exchange Coincheck, according to the Reuters report, which cited anonymous sources.

On Jan. 26, Tokyo-based Coincheck said someone hacked into its digital wallet and made off with more than 520 million units of a digital currency called XEM, affecting some 260,000 customers. The company admitted that they weren’t using all the necessary security measures, and promised to use its own money to reimburse customers. Japanese authorities announced that they would investigate all local crypto exchanges for security gaps following the breach.

North Korea is believed to be using cryptocurrency to get hard cash amid UN sanctions that are likely putting pressure on its cash reserves.

According to a September report from security firm FireEye, North Korean hackers targeted at least three South Korean crypto exchanges with the suspected intent of stealing funds last year, and one of the attacks was successful. When Seoul-based Youbit filed for bankruptcy after losing 17% of its assets in a cyberattack in December, South Korean investigators also looked into North Korea’s possible involvement in the hack.

The South Korean agency also briefed parliament on Monday that North Korea's theft of cryptocurrency from the South last year was on the scale of tens of millions of dollars. According to Korea Herald and Chosun Ilbo, citing a lawmaker, North Korea used bogus job application forms to hack customers' passwords.

The hacking at Coincheck is so far the biggest cryptocurrency theft on record. Tokyo-based Mt. Gox, which filed for bankruptcy in 2014 after lost about $480 million in a hack, was previously the largest heist.