Washington is limited in its response to N. Korea over Sony hack

WASHINGTON/SEOUL (Reuters) - President Barack Obama's threat of a "proportional" response to North Korea's hacking of Sony Pictures shows once more the limits of Washington's options as it seeks to rein in one of the world's most unpredictable and isolated countries.

U.S. authorities said on Friday investigators had determined that North Korea was behind the devastating cyberattack on Sony Pictures, setting up a further possible confrontation between the United States and the impoverished state.