It's not immediately clear if the Internet connectivity problems were an act of retribution for a major intrusion at Sony Pictures Entertainment that the FBI last week linked to North Korea.
President Barack Obama on Friday said the U.S. government would respond but didn't say how.
The White House declined to comment Monday. State Department spokeswoman Marie Harf told reporters that of the federal government responses, "some will be seen, some may not be seen."
Doug Madory (Muh-DOOR-ee), director of Internet analysis at Dyn Research, said the Internet connectivity problems were discovered in the last 24 hours and have gotten progressively worse to the point that "North Korea's totally down."
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