How on earth did North Korea build the bomb?

The first thing I did this morning, to find answers to this question, was google nuke bomb building...and surely that is what every U.S-hating Al-qaida wannabe will be doing as well - ';If some crazy 5'3'' dictator of an impoverished sanction-bound nation can build one, so can I!'; Surely this is the beginning of real proliferation - a bomb fest for terrorists.