Doug Madory, Dyn Research's director of Internet analysis said it was possible there was an innocent reason for North Korea falling off the Internet. But, "North Korea could be experiencing a DDOS (Distributed Denial of Service) attack."
But Madory added that North Korea's Internet has always been flaky. Still, Dyn has never seen North Korea's Internet fail quite like this before.
It's also possible that North Korea, in anticipation of an attack, has taken its connection down itself.
North Korea has a cyber-war capability but its Internet is tiny and tightly controlled by the government. Known by the name "Kwangmyong," it's connected to the world Internet via a single Internet service provider (ISP), Star-KP. The entire network has a mere 1,024 IPv4 addresses and 18 Web domains. It also has no IPv6 addresses. It may well be the world's smallest national Internet. To connect with the rest of the world, it relies on China Unicom, a People's Republic of China ISP.