American officials have alleged that North Korea's desperation for cash is driving a surge in cyber-attacks targeting banks and other businesses in the US and around the world.
The officials told American media house CNN that US-led sanctions on North Korea have squeezed its economy which lead to more cyber attacks.
The officials accused North Korea of using ransomware and electronic bank heists as part of their cyber attacks. They said that North Korea was also behind a cyber-attack on Bangladesh's central bank, back in 2016.
Hackers had stolen $81 million in that case.
Assistant Attorney General for US National Security at the Justice Department, John Demers, said North Korea has become a major cyber threat in recent years alongside Iran, China and Russia.
But unlike other countries, which focus more on intelligence operations, North Korea focus their energy on cash, he said.
"Straight up cyber bank theft -- that's a significant piece of what they do in cyberspace," Mr Demers told CNN.
US prosecutors first noticed North Korea's sophistication in cyber attacks in the 2014 hack of Sony Pictures Entertainment, in which hackers broke into the company's systems and began releasing embarrassing internal emails and documents in retaliation for a Sony movie that had satirised North Korean leaders.
In another scheme in 2017, hackers from North Korea orchestrated a series of WannaCry 2.0 ransomware attacks that infected computer systems around the world, including those of the British National Health Service, US, Australia and UK.