Posing as Americans, North Korean technology workers secured remote work contracts with hundreds of US companies as part of a scheme to help fund Pyongyang’s illicit nuclear weapons and missile programmes, the US government said on Thursday.

For three years, starting in October 2020, a US national named Christina Chapman of Arizona helped three North Korean IT workers obtain “illicit telework employment” using the identities of US citizens, earning about US$6.8 million, the State Department said.

More than 300 US companies were defrauded in the effort, the Justice Department said in a separate release, announcing charges against Chapman and other alleged co-conspirators.

“The charges describe a years’ long campaign by the North Korean government to infiltrate US job markets through fraud in an effort to raise revenue for the North Korean government and its illicit nuclear programme,” the Justice Department said.

Chapman not only helped steal US identities but ran a “laptop farm” by hosting computers issued by the US companies on behalf of the North Korean workers, the Justice Department said, operating them from her home so that it looked like the North Korean workers were based in the US.

She also allegedly helped launder the proceeds with her own financial accounts by receiving, processing and distributing their pay cheques, the department added. That resulted in US companies to filing false documentation to the Department of Homeland Security and false reports to the Internal Revenue Service.

The US also charged Oleksandr Didenko of Kyiv, Ukraine, with engaging in a years-long effort to create accounts using false identities at US-based freelance IT job search platforms and money service companies, according to the Justice Department. He ran a platform that allowed remote IT workers to “buy or rent accounts using identities other than their own on various platforms,” the department said.

Facing a raft of US and United Nations sanctions for its nuclear weapons and ballistic missile programmes, North Korea has turned to deploying IT workers overseas for government revenue, in addition to relying on cyberattacks and other online crimes, US and South Korean officials previously told Bloomberg.

The in-demand workers can make as much as US$300,000 a year working abroad, often working remotely through freelance platforms and using falsified or stolen identification, those officials said.

The US State Department’s Rewards for Justice programme is offering as much as US$5 million for information that leads to the disruption of efforts to fund North Korea’s weapons programme.

North Korea is also known to use fake job offers to trick US employees into providing sensitive information.

The development comes after North Korean hackers for years have targeted American companies, launching ransomware attacks and conducting cryptocurrency thefts, as another way to raise money for weapons programmes. Suspected North Korean hackers also stole slightly more than US$1 billion in cryptocurrency last year, according to the blockchain analysis company Chainalysis Inc.