Underestimating North Korea
A lot of people dismiss North Korea, thinking their threats and posing are just bluster. The cyber attack on Sony Pictures and the cancellation of the film "The Interview" have people rethinking their dismissive attitudes.
North Korea has not accepted responsibility for the hacks that have caused so much pain to Sony Pictures, and while most are pointing fingers at them, some do not believe the country is behind the attacks.
North Korea does, however, have a history of committing cyber attacks, most notably almost two years ago against South Korea. At the time, the North hit TV and banking computer systems.
Much of the code in the Sony Pictures attacks was used in the previous South Korean attack, and the malware code was written in Korean.
While it's pretty unlikely that North Korea will invade the United States with troops and planes as they did in the recent remake of "Red Dawn" it does look like their cyber warfare capabilities are more advanced than the US previously thought. Corporations and the American government would be well served to start ramping up cyber defenses.