the white house is labeling the attack on seen knee as a national security threat against the united states and promising a proportional response. u.s. investigators have concluded that north korea is behind the attack. we're also learning new details about a computer attack earlier this year. the source, another long-time adversary of the united states. cnn's brian todd is looking into this for us. what are you learning? >> wolf, many think the attack on sony was the first time that a foreign government tried to destroy the network of a company because it didn't like what that company said or did. we're learning new details on the attack of a casino operation in the world, an effort, allegedly, to punish that company for comments made by its chairman. a cascading attack, servers shut