Some send up plastic leaflets that weigh less than a feather and which flutter down from the clouds with calls for democracy, or blurry cartoons ridiculing North Korea’s ruler.
Some send flash drives loaded with South Korean soap operas, or mini-documentaries about the vast wealth of southern corporations, or crisp new US dollar bills.
One occasionally sends his empty food wrappers, with stained labels showing noodles slathered in meat sauce, so northerners can see the good life they would find in the South.
They are self-proclaimed soldiers in a quiet war with North Korea, a disparate and colorful collection of activists taking on one of the world’s most isolated nations, mostly using homemade hot-air balloons.
“The quickest way to bring down the regime is to change people’s minds,” said Park Sang Hak, a refugee from the North. Mr. Park now runs the group Fighters for a Free North Korea from a small Seoul office, sending tens of thousands of plastic fliers across the border every year.
Scholars and North Korean refugees say the outside information has helped bring a wealth of changes, from new slang to changing fashions to increasing demand for consumer goods in the expanding market economy.