Some file names gave away clues about the series and episode numbers. There were also files and projects the researchers could not identify—including a “bunch of files” with videos of horses and a Russian book on horses, Williams says.

Sanctions placed upon the North Korean regime, for its ongoing human rights abuses and nuclear warfare programs, prohibit US companies from working with DPRK companies or individuals. However, the researchers say it is highly unlikely that any companies involved would have a clue about North Korean animators working on the shows, and there is nothing suggesting the companies violated any sanctions or other laws. “It is likely that the contracting arrangement was several steps downstream from the major producers,” the report says.

Spokespeople for Amazon and Max spokesperson declined to comment for this story. YouNeek Studios did not respond to a request for comment.

“We do not work with North Korean companies, or Chinese companies on Invincible, or any affiliated entities, and have no knowledge of any North Korean or Chinese companies working on Invincible,” a spokesperson for Skybound Entertainment says. “We take any claims very seriously and have commenced an investigation into this.” In a post on X, the company characterized the findings as “unconfirmed” and said it is working with authorities to investigate.

Williams says it is possible that a front company in China is used to help disguise the activity and involvement of North Koreans. The researchers were able to analyze connections to the exposed server and, despite most having their location masked by a VPN, spotted access from Spain and three Chinese cities. “All three cities are known to have many North Korean–operated businesses and are main centers for North Korea’s IT workers who live overseas,” the report says.

While Williams says the researchers did not find any identifiable names of North Korean organizations buried in the files, the country has a well-established animation company called April 26 Animation Studio, which is also known as SEK Studio. Originally set up in the 1950s, the studio has worked on hundreds of international TV shows and movies.

However, in recent years, the US Treasury Department has sanctioned SEK Studios, individuals linked to it, and various “front companies” that it says are used to “work for foreign customers.” Many of these have links to China, according to the sanctions. “SEK Studio has utilized an assortment of front companies to evade sanctions targeting the government of the DPRK and to deceive international financial institutions,” a statement issued as part of the sanctions in 2021 says.

The main aim of these efforts, says Michael Barnhart, a North Korea researcher at Mandiant, is to raise money for the North Korean regime. The country’s hackers and scammers have stolen and extorted billions of dollars to help fund its military ambitions in recent years, including from huge cryptocurrency heists. In early 2022, the FBI issued a 16-page alert warning companies that remote North Korean freelance IT workers were infiltrating businesses to earn money they could funnel back home.

“The volume is much higher than we were expecting,” Barnhart says of North Korea’s IT workers. They are constantly changing their tactics to avoid being caught, he says. “We had one not too long ago, where during the interview, the person’s mouth was just off-frame. You could tell that someone in the background was speaking on their behalf.” Technically, Barnhart says, companies should verify their remote workers’ devices and make sure that there is no remote software connecting to a company laptop or network. Businesses should also put extra efforts at the hiring stage by training HR staff to detect possible IT workers.

However, he says, increasingly there is a greater crossover between North Korean IT workers and individuals who are members of known hacking groups or classified as advanced persistent threats (APTs). “The more we focus on IT workers, the more we’re starting to see APT operators and efforts blending in with those,” he says. “This might be the most quick learning-on-your-feet, nimble nation-state that I’ve ever seen.”