North Korea's Internet was back up Tuesday after a more than nine-hour outage, according to Dyn Research, a company that monitors Internet performance.
The disruption came amid an escalating war of words between the United States and North Korea over a massive cyberattack on Sony Pictures.
"Usually there are isolated blips, not continuous connectivity problems. I wouldn't be surprised if they are absorbing some sort of attack presently," Doug Madory, director of Internet analysis at Dyn Research, said when the Internet was down.
Matthew Prince, president of CloudFlare, a performance and security company, described the disruption as if "all the routes to get to North Korea just disappeared.
"It's as if North Korea got erased from the global map of the Internet," he said.
Prince, who also spoke when the Internet was down, told CNN it's well within the realm of possibility that a single individual could have been behind the interruption but said he can't conclude at this point that an attack took place.
"If it is an attack, it's highly unlikely it's the United States. More likely it's a 15-year-old in a Guy Fawkes mask," he said.
North Korea is accusing the U.S. government of being behind the making of the movie "The Interview."
And, in a dispatch on state media, the totalitarian regime warns the United States that its "citadels" will be attacked, dwarfing the hacking attack on Sony that led to the cancellation of the film's release.
While steadfastly denying involvement in the hack, North Korea accused U.S. President Barack Obama of calling for "symmetric counteraction."
"The DPRK has already launched the toughest counteraction. Nothing is more serious miscalculation than guessing that just a single movie production company is the target of this counteraction. Our target is all the citadels of the U.S. imperialists who earned the bitterest grudge of all Koreans," a report on state-run KCNA read.
"Our toughest counteraction will be boldly taken against the White House, the Pentagon and the whole U.S. mainland, the cesspool of terrorism," the report said, adding that "fighters for justice" including the "Guardians of Peace" -- a group that claimed responsibility for the Sony attack -- "are sharpening bayonets not only in the U.S. mainland but in all other parts of the world."
'Act of cybervandalism'
The FBI on Friday pinned blame on North Korea for a hack into Sony's computer systems.
In an interview broadcast Sunday on CNN, Obama called it "an act of cybervandalism," not war.
He said that the United States is going review whether to put North Korea back on a list of states that sponsor terrorism.
"We've got very clear criteria as to what it means for a state to sponsor terrorism. And we don't make those judgments just based on the news of the day," Obama said. "We look systematically at what's been done and based on those facts, we'll make those determinations in the future."
'Dishonest reactionary movie'
While the film was the work of private individuals, North Korea insisted otherwise in its statement. "The DPRK has clear evidence that the U.S. administration was deeply involved in the making of such dishonest reactionary movie," it said.
"The Interview" is a comedy, with plans for an attempted assassination of North Korean leader Kim Jong Un a central plot point.
In a CNN interview on Friday, Sony Entertainment CEO Michael Lynton said the studio had not "given in" to pressure from hackers and was still considering ways to distribute the movie.
But that's not what the company initially said after canceling the film's release.
On Wednesday night, a studio spokesperson said simply, "Sony Pictures has no further release plans for the film."