Key North Korean websites were back online Tuesday, but the outage in one of the least-wired countries in the world was probably more inconvenient to foreigners than to North Korean residents – most of whom have never gone online.
Even for wired Koreans south of the heavily armed border separating the rivals, the temporary outage made little difference: Southerners are banned by law from accessing North Korean websites.
The shutdown followed a U.S. vow to respond to a crippling cyberattack on Sony Pictures that Washington blames on Pyongyang. The White House and the State Department declined to say whether the U.S. government was responsible.
(Read more: Why do Americans think North Korea is behind the Sony hack? Read the FBI's full statement)
WHAT HAPPENED TO NORTH KOREA'S INTERNET?
South Korean officials, speaking on condition of anonymity because of office rules, said the North's official Korean Central News Agency and the Rodong Sinmun newspaper, which are the main channels for official North Korea news, had earlier been down. But the websites were back up later Tuesday.
U.S. computer experts described the Internet outages in the North as sweeping and progressively worse. Jim Cowie, chief scientist at Dyn Research, an Internet performance company, said in an online post that the North came back online after a 9 1/2-hour outage.
WHAT CAUSED THE SHUTDOWN?
Possible causes for the shutdown include an external attack on its fragile network or even just power problems, Cowie wrote. But, he added, "We can only guess."
HOW DOES THE NORTH KOREAN INTERNET WORK?
Only a very small number of people among North Korea's elite use the Internet, as the rest of the world knows it. A slightly larger group of privileged North Koreans can see a tightly controlled Intranet called Kwangmyong, meaning "Bright." On this self-contained, authoritarian alternative to the World Wide Web, chats and e-mails are monitored and content comes pre-filtered by the state.
The intranet provides a connection between industry, universities and government. Its role seems to be to spread information, rather than for commerce, entertainment or communication, Will Scott, a computer science instructor at Pyongyang University of Science and Technology, told AP in February.
Most common North Koreans probably don't actively use Kwangmyong because owning a computer requires permission from government authorities and would cost as much as three months' salary for the average worker, Seo said.
HOW MANY HAVE ACCESS?
Internet: It is unclear how many Internet-connected devices are used in North Korea. But it's likely that the number of Internet users is small considering that the country has only 1,024 Internet Protocol addresses for a population of 25 million, according to So Young Seo, a researcher at South Korea's state-run Korea Information Society Development Institute.
Mobile devices: Cellphone use in North Korea is also controlled by the government. While mobile phones are now a popular gateway to the Internet in the South, for North Koreans cellphones are used for domestic calls. They can't access the Internet or make overseas calls. More than two million cellphones are used in North Korea, according to the International Telecommunication Union. But the number of mobile users is believed to be significantly smaller, Seo said, because elite North Koreans often use more than one device because it's cheaper to buy a new phone than buy additional minutes on the same handset.
3G networks: In 2013, North Korea began to allow foreigners to access the Internet through the 3G networks. They could upload posts or photos on Twitter and Instagram from North Korea. Starting last year, North Korea began selling monthly mobile Internet data plans to foreigners for use with a USB modem or on mobile devices using their SIM cards. Orascom built a 3G network more than five years ago. The network now covers most major cities.
HOW DOES THE NORTH KOREAN STATE USE THE INTERNET?
North Korea's use of the Internet targets outsiders more than residents, who still mostly rely on traditional outlets for information and entertainment.
Various North Korean government bodies have launched websites as well as English-language Facebook pages, YouTube channels and Twitter accounts to spread propaganda aimed at international audiences. The North uses social media to praise its system and leaders, and to repeat commentaries sent out by the country's official Korean Central News Agency.
HAS NORTH KOREA BEEN HACKED BEFORE?
In 2013, some of the social media accounts run by North Korea were hacked by those who purported to be part of the hacker activist group Anonymous. Hackers left a message on Twitter and posted a picture of the North Korean leader's face with a pig-like snout and a drawing of Mickey Mouse on his chest.
In another attack, Pyongyang saw intermittent Internet access for two days in March, 2013. North Korea blamed the shutdown on the United States and South Korea, accusing the allies of "intensive and persistent virus attacks." South Korea denied the allegation and the U.S. military declined to comment.
WHO WOULD BENEFIT FROM HACKING NORTH KOREA?
A cyberattack on North Korea would be an exercise in futility if the purpose was to cause a serious disruption, said Chang Yong Seok, a North Korea expert at Seoul National University.
"Even if their Internet is shut down, the inconvenience will be shared only by members of the power elite," Chang said. "It would be an entirely different matter if hackers manage to penetrate the Kwangmyong network, but that has never happened before."
WHAT DOES THE SONY HACK HAVE TO DO WITH IT?
Though it denies responsibility for the Sony hack, Pyongyang has called it a "righteous deed" and made clear its fury over The Interview, a comedy that depicts the assassination of the North's authoritarian leader, Kim Jong-un, the head of a 1.2 million-man army and the focus of an intense cult of personality.
President Barack Obama has said the U.S. government expected to respond to the Sony hack, which he described as an expensive act of "cyber vandalism" by North Korea. Obama did not discuss details, and it was not immediately clear whether the Internet connectivity problems represented the retribution. The U.S. government regards its offensive cyber operations as highly classified.