They’ve become symbols of the drive of many human rights activists, particularly in South Korea, to see freedom in North Korea in their lifetimes: balloons, packed with everything from bibles to USB drives with South Korean soap operas to pro-democracy literature to Choco Pies for the hungry.

Proponents of the balloons say they are breaking North Korea’s strict control of information, and opening the minds of North Koreans to information from outside the country.

But how effective are they in bringing change to North Korea, and what are the risks involved?

The use of balloons to get information into closed-off