June 24, 2015:
It was recently revealed that the American-Israeli Stuxnet computer virus that successfully got into Iranian uranium processing facilities and during 2010 did a lot of damage, was not able to penetrate North Korean security. The computer networks in the Iranian facilities, like the North Korean ones, are not connected to the Internet and Stuxnet got in by hiding on memory sticks (USB memory drives) and it was possible to distribute enough infected memory sticks in Iran so that one or more got plugged into a PC on the procession facility network. No such luck in North Korea, where security was much tighter and far fewer people have any access to, or experience with, PCs or memory sticks. There are also a lot fewer Internet users in North Korea and most of those who do have access can only use one that only connects to sites inside North Korea.