Included among the forbidden foreigners are the Chinese of Korean ancestry that live across the northern border. These Korean speaking Chinese provide support for North Koreans who manage to flee across the border. Getting caught, on the North Korean side, trying to get out is a jail, or firing squad, offense. But China has been getting richer over the last two decades, partly by mass producing inexpensive consumer goods. Among these are cheap radios, as in less than a dollar. These cheap radios have been finding their way into North Korea, and the communist government there is very upset. As a result of those radios, and a power shortage that prevents the government radio jammers from drowning out foreign broadcasts, fear is growing among the few percent of the population that runs North Korea. Fear that the people are finding out that the rest of the world is a lot richer than North Korea, and not run like a huge prison camp.
Christian missionaries have led the effort to smuggle bibles, and radios, into North Korea. The penalty for getting caught doing this is death. But still the cheap, tiny radios come, and it's only a matter of time before enough North Koreans figure out they've been had.
North Koreans live under the most restrictive government in the world. Any contact with foreigners is strictly regulated. Get caught have unauthorized contact with foreigners and you got to jail, labor camp or execution. This contact includes foreign newspapers, and radio broadcasts. Only radios tuned to the state radio station are allowed in North Korea.