North Korea is stepping up its cyber capabilities to target international aerospace and defence industries through a shadowy and sophisticated hackers group called Reaper, a new report revealed on Tuesday.

The group, also known as APT37, was identified in research by American private security company FireEye, which tracks cyber-attackers around the world.

They reported that it is using malware to infiltrate computer networks and now represents “an advanced persistent threat” that has dramatically increased the reach of North Korea’s already formidable cyber operations.

Fears have been rising for some time about a growing North Korean cyber army of an estimated 6,000 hackers, handpicked by Pyongyang’s cyberwarfare agency, Bureau 121, and trained to plunder international banks, military espionage and to attack critical infrastructure.

The latest analysis by FireEye describes APT37 as an “additional tool” in Pyongyang’s online armoury, claiming that the group’s activities are “expanding in scope and sophistication,” and will likely be used further.

“We assess with high confidence that this activity is carried out on behalf of the North Korean government,” the report says. “We judge that APT37’s primary mission is covert intelligence gathering in support of North Korea’s strategic military, political and economic interests.”

FireEye believes APT37 was founded in 2012 and is based in North Korea. From 2014 to 2017, its hackers concentrated primarily on the South Korean government, military defence, industrial base and media sectors.