The agency said tech workers from North Korea were pretending to be from other countries in Asia to obtain remote work and raise funds for the regime.
The FBI has warned businesses against inadvertently hiring remote tech workers from North Korea.
An advisory notice issued by the American security service along with the US State and Treasury departments warned rogue freelancers were taking advantage of remote work opportunities to hide their true identities and earn money for Pyongyang.
The United States said the effort was intended to circumvent US and UN sanctions against the dictatorship, and bring in money for North Korea's nuclear weapons and ballistic missile programmes.
"There are thousands of DPRK IT workers both dispatched overseas and located within the DPRK, generating revenue that is remitted back to the North Korean government," the advisory stated.
"These IT workers take advantage of existing demands for specific IT skills, such as software and mobile application development, to obtain freelance employment contracts from clients around the world, including in North America, Europe, and East Asia".
The notice added that many North Korean workers pretended to be from South Korea, Japan, or other Asian countries.
“The United States is committed to disrupting illicit DPRK revenue-generating activities, which may facilitate criminal activity, provide direct support to the DPRK’s unlawful weapons of mass destruction (WMD) and ballistic missile programs, and threaten international peace and security,” read a statement from US State department spokesman Ned Price.
The advisory set out a series of red flags that employers should watch for. These include a refusal to participate in video calls, requests to receive payments in virtual currency, frequent money transfers via payment platforms, and multiple logins to an account from various IP addresses in a short period of time.
US officials said the North Koreans were mostly based in China and Russia, with smaller numbers operating out of Africa and Southeast Asia.
Much of the money they earn is taken by the North Korean government, they said.
The officials also said that companies who hired and paid such workers may be exposing themselves to legal consequences for sanctions violations.