The White House says the devastating cyber attack on Sony Pictures was done with "malicious intent" and was initiated by a "sophisticated actor" but it would not say if that actor was North Korea.

Spokesman Josh Earnest says the matter is still under investigation.

"Regardless of who is found to be responsible for this, the president considers it to be a serious national security matter," Earnest says.

President Obama is holding daily meetings with his homeland security advisers and cyber coordinators to determine who is responsible and how to respond. Whatever action is taken, says Earnest, it needs to be "proportional."

"They are considering a range of options," he says. But he adds that the president is also "mindful of the fact sophisticated actors are often times seeking to provoke a response from the United States of America. They may believe that a response from the U.S. in one fashion or another would be advantageous to them."

Intelligence officials have turned their attention to North Korea this week as the likely culprit. But some have said the attack may also have come from inside Sony, possibly with the help of someone who has worked there.

Sony Pictures canceled the release of its $44 million comedy "The Interview"after hackers threatened there would be attacks on theaters that showed the film. The apparent hackers said they were incensed by the film that depicts the North Korean leader's head being blown off.

In a message posted to the file-sharing site Pastebin, the alleged hackers wrote — in awkward English — a warning to movie goers.

"Soon all the world will see what an awful movie Sony Pictures Entertainment has made.The world will be full of fear.Remember the 11th of September 2001.We recommend you to keep yourself distant from the places at that time.(If your house is nearby, you'd better leave.)"

James Lewis, a senior fellow with the Center for Strategic and International Studies tells NPR's Mellissa Block that the attacks are unprecedented.

"It's the combination of the techniques and the vindictiveness and the duration of the attack that make it special," says Lewis, who has worked for the state and commerce departments.

Lewis says North Korea has been pursuing cyber warfare for almost 20 years.

"The current leader's father put big emphasis on building an IT industry," he says. "They probably have several thousands of people who are part of their intelligence service. They've improved markedly over the past 10 years."

Lewis says, if North Korea is responsible, as most in the intelligence community seem to believe, this attack has a political agenda.

"This is not warfare, this is politics," he says. "North Koreans are very touchy about their leaders. They've gone after banks, TV stations, newspapers, government agencies. It's part of a larger political campaign to make a political point or defend their leaders' reputation."

The White House defended the right of writers and artists to freely express their views, even those they do not agree with. "And while we may not agree with the content of every single thing that is produced," Earnest says, "we certainly stand squarely on the side of the right of private individuals to express themselves."

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