Back in 1950s through 1990s until 15th President of Republic of Korea, Daejung Kim launched the "Sunshine Policy", the confrontation between South an North Korea can be represented as the "War of Propaganda". Not only did the North Korea severely controlled their broadcasting to the people, but also South Korean government rarely permits its Freedom of Expression to people. I remember when I was in elementary school attending a society class around early 1990s, a teacher taught us that we should not to write anything that is pro to North Korea. The teacher was warning us if we write anything good on North Korea, police will come and captivate us to jail. I believe I was only nine years old back then. Afterwards, teacher taught us how good the democracy is and how evil the communism is. At that time since I was young I do not have any idea what the democracy and communism are. I just accept what teacher taught us which we do not have any right to do anything that against our democratic government.
In North Korea, apparently, broadcast mainly through two channels one is for Chosun Chungang TV(Chosun Central TV) for domestic/ South Korea and Chosun Education and Culture for domestic North Korean. North Korea broadcast for 6 hours a day. Not surprisingly, it is strictly controlled by the government. Most of contents are about their identity as a communism, nationalism and praising their leader, Kim Il-sung and Kim Chung-il. It is said that apparently North Koreans can see the South Korean's soap opera. Well, this could be good and bad because North Koreans can get a glimpse of different world from their own country through the soap opera but they also can hold the negative bias towards the westernized South Korean society which they regards evil things.
Besides the television, North Korea use the radio for their propaganda. Most of North Koreans do not have TV in their home and they even cannot afford the electricity for television. By using the short wave radio, North Korea can transmit their propaganda to South Koreans. However, using radio does not seem to be good enough anymore for North Korea to reaching the South Koreans since radio is not favorite communication mechanism for South Koreans.
These days, North Korea uses the internet method for the communication. They create the internet website, www.uriminzokkiri.com which offers in Korean and Russian (it is interesting that they do not offer the webpage in English). They also using the Social Media such as YouTube or Twitter. On Twitter, most of the followers comment for warning the United States or South Korea. They are using very strong words for instance, diminish, demolish, fight and so on against the South Korean government. They also put some videos on You tube mostly show how good the North Korea and their leader are.
In any forms of North Korean's communication is fully controlled by the government. There is a research for the communication in North Korea: http://northkoreanmediastructures.wordpress.com/north-korea-media-structure-list/
The communication in North Korea is really unique and actually, it is one-way communication in order to control over the people. It is really unique when this way of communication actually well worked out for last 60 years. However, it seems that North Korea does not that effectively communicate to South Koreans.