North Korea has a history of being an enigmatic country, where few foreigners are welcome or allowed to stay. Those that do are under close surveillance. 

Yet the country remains a focus of considerable interest for neighbors near and far. China, Russia — the two great powers at North Korea’s border — along with the United States remain particularly interested in knowing what is happening, and they are well placed to carry out detailed surveillance operations. 

The same goes for South Korea, where fears of military conflict on the peninsula drive much of the collection effort