North Korea's internet temporarily blacked out

North Korea experienced sweeping and progressively worse internet outages extending into Monday, with one computer expert saying the country’s online access at one stage went “totally down”.

The White House and the Department of State declined to say whether the US government was responsible amid tensions over the massive hacking of Sony and cancellation of The Interview, a comedy sending up regime leader Kim Jong-un.

By Tuesday, the US-based internet monitoring company Dyn said North Korea appeared to be back online. But “the question is whether it will return to the unstable fluctuations we saw before the outage”, said Dyn spokesman Jim Cowie.

Internet technology service Arbor Networks, which protects companies against hacking, said its monitoring detected denial-of-service attacks aimed at North Korea’s infrastructure starting on Saturday and persisting on Monday. Such attacks tie up a target’s internet equipment so that it becomes overwhelmed until the attacks stop or the spurious traffic can be filtered and discarded to allow normal connections to resume.

Given North Korea’s limited connectivity and lack of internet sophistication, it would be relatively simple for a band of hacktivists to shut down online access, and it should not be assumed that the US government had any part, said Dan Holden, director of security research at Arbor Networks. “Anyone of us that was upset because we couldn’t watch the movie, you could do that. Their internet is just not that sophisticated.”

Barack Obama said on Friday that the US government expected to respond to the hacking of Sony Pictures, which he described as an expensive act of “cyber vandalism” that he blamed on North Korea. The president did not say how the US might respond, and it was not immediately clear if North Korea’s internet connectivity problems were in retribution. The US government regards its offensive cyber operations as highly classified.

“We aren’t going to discuss, you know, publicly operational details about the possible response options or comment on those kind of reports in any way except to say that as we implement our responses, some will be seen, some may not be seen,” state department spokeswoman Marie Harf said.

North Korea has forcefully denied responsibility for hacking Sony.

Doug Madory, the director of internet analysis at Dyn, said the problems were discovered over the weekend and grew progressively worse until North Korea went “totally down”.

He said one benign explanation for the problem was that a router suffered a software glitch, though a cyber-attack involving North Korea’s internet service was also a possibility.

Routing instabilities were not uncommon but this particular outage was prolonged and got worse instead of better over the hours, Madory said.

“This doesn’t fit that profile,” of an ordinary routing problem, he said. “This shows something getting progressively worse over time.”

North Korea is one of the least connected countries in the world. Few North Koreans have access to computers, and even those who do are typically able to connect only to a highly regulated and censored domestic version of the internet that is not linked to the outside world.

Only a small approved segment of the population has any access to the world wide web via broadband.

North Korean diplomat Kim Song, asked on Monday about the internet problems, told the Associated Press: “I have no information.”