Cheap tiny radios are flooding North Korea.
They are either coming over the border from China, or being smuggled in by weather balloon from the South. In any event, these radios CAN get South Korean radio broadcasts, they are tiny enough to be concealed almost anywhere, they are solar-powered, so they don't require batteries, and they cost only a couple of bucks each.
Information is power. When enough of the North Koreans know the score, the regime will be overthrown.