Well
The North Koreans are Koreans like the South Koreans. Literacy for 2000 or more years.
Plus they consider themselves still at war with the US and the south. Their military has very serious amounts of artillery, special operations units, submarines and even some Mig29s.
As with any serious military, they have a competent long-range reconnaissance capability which does all sorts of nefarious electronic things. Just like every other serious power does. Not just hacking.
Finally, we should refrain from believing all the BS fed to us by our own media about North Korea. Some of it was clearly hyperbolic. For example, they seem to have successfully latched onto the Chinese economic miracle. A lot of things which have "made in China" printed on, must be suspected to be actually made in North Korea.