South Korean and US authorities warned businesses against inadvertently hiring information technology staff from North Korea who mask their true identities to skirt international sanctions and earn cash. The two allies say the IT staff are being employed to bankroll the isolated country’s nuclear and missile programs.

The joint advisory on Thursday, which follows previous warnings in May and December last year, includes fresh instructions to prevent North Korean freelancers from obtaining jobs at global tech companies, the Foreign Ministry in Seoul said in a statement.

If companies suspect cheating by applicants during the hiring process and find applicants speaking a language or living in a place different from that written in their application, hiring managers should think twice before deciding to offer them employment, according to the statement.

If employees demand to be paid for work through other means than a bank account or use a trucking or shipping company as their primary address, employers should check if the employees are who they say they are, the statement added, calling for tougher background checks and internal security within firms.

“The measure today aims to raise awareness of these North Korean IT workers around the world,” a senior official in Seoul said, noting that hiring them is a violation of not only United Nations Security Council resolutions, but also regulations in both Korea and the US.

Accepting services offered by North Koreans without approval in advance from the South Korean government could lead to a prison sentence of up to three years or 30 million won ($22,100) in fines. The Foreign Ministry urged people to alert the spy agency and police if they pick up on something suspicious. The three agencies have been working with the US State Department and FBI on the issue.

Because of security protocols, the Foreign Ministry has so far avoided revealing how those highly skilled workers have passed application processes and whether the companies that have hired them suffered any real damage. Cybercrimes -- from distributing malware to brazen attacks on financial systems -- have been a regular practice for some time for Pyongyang.