Sony hack: White House views attack as security issue
A cyber attack on Sony Pictures that forced the cancellation of a major film release is being seen as a serious national security matter, the US says.
A White House spokesman said the US believed the hacking was the work of a "sophisticated actor" - but refused to confirm if North Korea was responsible.
Sony withdrew The Interview, a new comedy film about North Korea's leader, after threats from hackers.
Hackers have already released sensitive information stored on Sony computers.
Jon Sopel reports.