As the international community looks for new ways to punish North Korea for its latest nuclear test, one area is emerging as the next front to apply pressure: North Korea's practice of sending workers overseas to earn money for the regime.
The United States and South Korea had already started quietly trying to persuade host countries to stop allowing in North Korean guest workers, according to people who work in both governments.
That drive is likely to accelerate now that North Korea has shown that new sanctions imposed this year have failed to dissuade it from pursuing nuclear weapons.
"There's going to be a global shaming campaign," said Andrei Lankov, an expert on North Korea at Kookmin University in Seoul, citing conversations with officials.
In the five years since Kim Jong Un took over, North Korea has dramatically stepped up the number of people it sends abroad to earn hard currency.
At least 50,000 North Koreans - and by some estimates, double that - are working in more than two dozen foreign countries. The vast majority, about 80 per cent, are in China and Russia, toiling in garment factories and on construction sites, or felling trees in Siberian forests.
There have also been numerous reports of North Korean doctors working in Cambodia and Libya, sculptors building statues in Senegal and Namibia, and labourers on building sites in Mongolia and in the soccer stadiums of Qatar.
The North Koreans are sent abroad usually for three years and are still tightly controlled outside the totalitarian country.
At one garment factory in northern China, visited by a Washington Post reporter last year, North Korean women lived in small dormitories inside the factory and were allowed to go out to the market only once a week and only in small groups - so they could keep an eye on one another.
While they're abroad, the North Koreans are allowed to keep one-third of their earnings - or US$100 out of their monthly US$300 salary for the seamstresses in China - and the rest goes to the regime. The Seoul-based Database Centre for North Korean Human Rights estimates that the Kim regime now earns US$300 million a year this way.
This is a considerable amount for North Korea. Its exports to China, by far its largest trading partner, totalled US$227 million last year, according to South Korea's International Trade Association.
Given that North Korea's main exports - mineral resources like coal and iron ore - were explicitly banned under UN sanctions imposed in March following the previous nuclear test, analysts expect Pyongyang to become increasingly reliant on labour to generate hard currency.
That's where the "shaming campaign" comes in.
The international community is now talking about more sanctions against North Korea. "We will be working very closely in the Security Council and beyond to come up with the strongest possible measure against North Korea's latest actions," Sung Kim, the American point man on North Korea, told reporters in Tokyo.
But after years of sanctions, many analysts say there is little left to target. And it will be difficult to designate host countries directly, so American and South Korean diplomats have been using behind-the-scenes pressure.
"We have raised with some governments our concerns about the use of [North Korean] workers in their countries, and consequently some governments have modified their policies," the State Department said in a report sent to Congress late last month.
South Korea has been doing the same. "We've been trying to explain to these countries that this [labour export] is not good for the North Korean people and that it's aiding the North Korean regime," said Kim Dong Jo, a spokesman for President Park Geun Hye.
Seoul can take the moral high ground now that it has closed down the Kaesong industrial complex, where North Koreans worked in South Korean-owned factories, and which contributed US$120 million last year to the regime's coffers.
The new campaign has already paid some dividends.
Malta, the smallest country in the European Union, effectively expelled some 20 labourers who had been working on construction sites and in garment factories in July by declining to extend their work permits.
Poland stopped issuing visas for North Korean workers following the nuclear test in January, the Voice of America radio station reported in June, quoting a Polish foreign ministry official. Poland had granted visas for 156 North Koreans in 2015, mainly to work in its shipyards.
But the campaign also faces some inherent constraints. For one, China and Russia, the hosts of the vast majority of the workers, have not traditionally seemed to worry about what other countries think of them.
Analysts are divided on the merits of clamping down on North Korea's labour exports.
"I think that there is clearly a benefit to allowing North Koreans to experience something of the outside world," said Go Myong Hyun, a research fellow at the Asan Institute for Policy Studies in Seoul and the author of a 2014 report on North Korean labour exports. "But the downside is great."
Some of the income is going towards North Korea's developments of weapons of mass destruction, Go said. "This money isn't just being spent on toys for Kim Jong Un."
Yang Moo Jin, a professor at the University of North Korean Studies in Seoul, said the benefit of exposing North Koreans to the outside world, even if only a sliver, was worth the cost of potentially funding the nuclear and missile programmes.
"I believe that the more that North Koreans experience working overseas, the higher the chance of North Korea changing," Yang said, noting that the workers might learn how rich South Korea is and how advanced South Korean products are. "There could easily be 200,000 North Koreans who now have a different, positive view of South Korea."
Lankov said that overseas labour was far more lucrative than work at home, where the average salary for a government official is less than US$10 a month. Returning to North Korea with even US$1000 or US$2000 could be transformational in a country tentatively moving towards marketisation.
"These workers return with a few thousand dollars, an amount of money that is sufficient to start a small business in North Korea," Lankov said.
I think that there is clearly a benefit to allowing North Koreans to experience something of the outside world
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This trend has created a little bit of freedom in North Korea, with the reliance on markets to provide what the state no longer can, slightly weakening the regime's control over the North Korean populace.
But Choi Yoon Cheol, secretary general of the North Korea Strategy Centre, a defector-led advocacy group based in Seoul, thinks the costs are too great.
"Yes, there's a positive side to this," he said. "But the money can also be a source for developing the missile and nuclear programmes. We should make stopping this our priority."
China - the most important country in this situation - has voiced clear anger over the recent nuclear and missile tests, but its priority remains ensuring stability on its borders.
"China has their own reasons why they don't want this," said Kim Byung Yeon, a professor at Seoul National University who focuses on the North Korean economy. "If China agrees to reduce the number of workers, they'd just have to give North Korea more aid."