The messages are alluring, the pictures are attractive. But the women seeking to beguile South Korean Bitcoin executives could actually be hackers from Pyongyang in disguise, experts warn.

In the face of sanctions over its banned nuclear and ballistic missile programmes, the cash-strapped North is deploying an army of well-trained hackers with an eye on a lucrative new source of hard currency, they say.

Its cyberwarfare abilities first came to prominence when it was accused of hacking into Sony Pictures Entertainment to take revenge for "The Interview", a satirical film that mocked its leader, Kim Jong-Un. 

But it has rapidly expanded from political to financial targets, such as the central bank of Bangladesh and Bitcoin exchanges around the world, with Washington this week blaming it for the WannaCry ransomware that wreaked havoc earlier this year.