I'm a little confused by the news stories about this. Did he take down their country-wide network, or just the few lines in and out of the country? It seems like he just hit a few NK websites and they everything stopped responding to him. Its like cutting the uk-europe power links and saying you took down all of the UK's power infrastructure
Only the lines in/out. NK has their own intranet which is completely separate from the global internet, which was presumably entirely unaffected by this.