US authorities are warning that a North Korean-controlled hacking team called the BeagleBoyz has stepped up its attacks on banks around the world, attempting multiple fraudulent money transfers and ATM cash outs.

A UN report last year estimated that North Korea has generated $2 billion in revenues for its weapons programme through the state-sponsored looting of financial institutions and cryptocurrency exchanges.

A US alert earlier this year listed a host of acts believed to have been carried out by the North Koreans, including the 2016 Bangladesh Bank heist, the WannaCry ransomware campaign, the FASTCash ATM cashout scam, and a $250 million digital currency exchange hack.

And while the hackers appear to have gone quiet last year, they have resumed their attacks since February, warns a new alert put out by the FBI, US Treasury, US Cyber Command and the Cybersecurity and Infrastructure Security Agency.

In particular, a team called the BeagleBoyz is posing "severe operational risk for individual firms," says the alert, citing a 2018 attack on a bank in Africa which could not resume normal ATM or point of sale services for its customers for almost two months following an attempted FASTCash incident.

The gang has targeted banks in dozens of countries over the last five years, netting hundreds of millions of dollars for the North Korean regime, says the alert.