Should North Korea's Threats Alarm Us?

North Korea has threatened strikes against "the whole US mainland" after the US accused it of being behind a massive cyber-attack on Sony Pictures. North Korea has denied responsibility for the attack, but what is known about its cyberwarfare potential? And what should the US and others do to prevent similar attacks?

(Photo: Painting of North Korean soldier holding a gun. Credit: Robyn Beck/AFP/Getty Images)