The web servers of three television networks and three major banks in South Korea were brought down by cyber attacks earlier today and, naturally the first suspected culprit is North Korean hackers. Website and ATMs were offline for several hours and even some employees at the TV stations where not able to get their computers up and running. Police called the attack "pretty massive" and the TV stations were still struggling to get web operations back online. (Their broadcasts were not affected.)
South Korea military officials did not explicitly blame the North for taking down their sites, but they did raise their readiness level in response to the outage. Just last week, it was the North that was accusing the South (with some help from the United States) of launching cyber attacks on their website, continuing the escalating back-and-forth. The North also had their share of internet outages last week, that also appeared to have been the result of deliberate attacks.
The North has had some success in the cyberwar realm, launching massive denial of service attacks on the South in 2011. We suppose that if the two sides are going to fire more "shots" at each other, it's probably better if they fight their new war online and not in the DMZ. Even so there could be other culprits, including China or even hackers unaffiliated with any nation.