The reclusive country known as North Korea is said to be in possession of a GPS jamming device that can disrupt signals that occur across a wide area, in fact, including those that are more than 100km away. To date, the North did disrupt signals in South Korea from Kaesong and Mt. Kumgang several times already, and the communist country has also deployed vehicle-mounted jammers that are capable of disrupting signals within 50-100km. Just where did these vehicle-mounted jammers come from? Well, they were imported from Russia at the turn of this century, and most of them see action near the Demilitarized Zone.
It is said that North Korea has close to 20 kinds of communications and radar jamming devices which they imported from the former Soviet Union, and I wonder whether some stolen technology from other countries not friendly with the North are there as well.
Perhaps if South Korea ever wants to put their foot down and decide to reunite both Koreas as a single peninsula, they might look towards the new EMP bomb that they built and unleash it prior to a carefully planned invasion.