They are not widely known. And their chances at achieving their stated aim — overthrowing the North Korean government — are believed to be slim at best.
Yet the defector group that calls itself Free Joseon (Free North Korea) could be the first organization to have successfully infiltrated a North Korean diplomatic mission.
Last week, Free Joseon claimed responsibility for a Feb. 22 raid on Pyongyang's embassy in Madrid. Ten intruders armed with knives and replica pistols entered the embassy, according to Spanish authorities.
They say the Free Joseon operatives tied up North Korean diplomats and made off with computers, cellphones and other equipment — and flew to the U.S., where the group's leader shared information with the FBI. The U.S. has denied involvement in the raid.
Pyongyang's first public acknowledgment of the incident came on Sunday, when it complained North Korea had been the victim of a "grave terrorist attack" in which its diplomats were beaten and tortured, calling it a "flagrant violation of international law." It called on Spanish authorities to thoroughly investigate the incident and bring the perpetrators to justice.
Normally, says Sung-Yoon Lee, a Korean studies expert at the Fletcher School at Tufts University, North Korea would be loath to mention anything at all that might puncture "the myth of invincible, unassailable, infallible, omnipotent leadership." But these days, too much information is flowing into North Korea for its government to keep the Madrid embassy incident a secret.
Two years ago, under a different name, the group was apparently successful in spiriting away to safety a potential heir — or possible threat — to the Kim dynasty. Last month, rebranded as Free Joseon, it made a declaration of revolution and announced the establishment of a "provisional government" to take power in Pyongyang.
The group has raised the flag of rebellion at a particularly sensitive time, when the U.S. and South Korean governments are committed to a policy of negotiating and engaging with Pyongyang. The embassy incident took place just days before President Trump met with North Korean leader Kim Jong Un in Vietnam.
The group first came to light in 2017, following the assassination of Kim Jong Un's half-brother Kim Jong Nam in Malaysia, which some South Koreans suspect was ordered by Kim Jong Un. Under the alternate name Cheollima Civil Defense (Cheollima is the Korean equivalent of Pegasus, the winged horse in Greek mythology), it claimed it had taken Kim Jong Nam's son Kim Han Sol under its protection. Kim Han Sol has not been seen in public since appearing in a 2017 Cheollima Civil Defense video.
Last month, on the 100th anniversary of Korea's independence movement against Japanese colonial rule, Cheollima Civil Defense resurfaced as the rebranded Free Joseon. On March 1, it posted a YouTube video in which a woman, whose face is obscured, reads the group's declaration of revolution and the establishment of a government in exile.
"We the people of North Korea," she says, "indict this immoral and illegitimate regime for the starvation of millions, despite the ability to feed them, for government-sponsored murder, torture and imprisonment."
Lee says there are no signs of imminent regime collapse, and defector groups are no match for North Korea's mighty security apparatus. But throughout history, he notes, revolutionaries who fail have often inspired others who eventually succeed.
Even if the Pyongyang regime eventually falls, "The entire government system will not be eradicated," says Kim Jung-bong, a former official with South Korea's National Intelligence Service. "I think a new government will emerge from within North Korea."
Nevertheless, the raid on the Madrid embassy has fired up North Korean defector groups in South Korea, none of whom have yet dared to call for armed resistance against Pyongyang.
Park Sang Hak, director of a Seoul-based umbrella group called the Association of North Korea Human Rights, expresses envy of his fellow defectors in the Free Joseon group, which he believes has "the help of the U.S. government." (A State Department spokesman last week said the U.S. "had nothing to do with" the Madrid raid). "But we are being oppressed by the current [South Korean] administration," Park says. "I sometimes wonder if I'm in Seoul or in Pyongyang."
Some defectors have complained that, in its eagerness to engage with Pyongyang, the administration of South Korean President Moon Jae-in has tried to silence them or cut funding for their group's activities. The South Korean government rejects these allegations.
Park says he has previously worked with Adrian Hong Chang — the Mexican citizen named by Spanish authorities as the leader of the raid on the Madrid embassy — distributing propaganda leaflets into North Korea.
"He's less like the leader of a civic group, and more like a soldier on a battlefield, bold and combative," he says. "He's a very charismatic leader."
Free Joseon says on its website that it is suspending operations for now, due to negative media coverage. But it urges patience, and says it is planning big things for the future.