SECOND UPDATE: The issue appears to be that there were initially reports that a Japanese site was attacked and that the VANK attack was in retaliation. Latest reports, such as this from JoongAng Daily, state that it is actually just comments about the skaters bombarding Japanese sites that prompted 2ch.net to alert users how to attack VANK. I posted the information because it's interesting, but I cannot state that any of it is fact. We might never know how the attacks started or who was really attacked, as that is often the nature of cyberattacks. I will also add that I haven't seen anything in any of these articles to substantiate VANK's assertions.
UPDATE: Some commenters are saying that this information isn't true, but I only know what the news says and it is including the VANK chairman's assertions regarding the attacks. So here is an article from The Korea Times (the link is not highlighting in Firefox for some reason but you can click it anyway!) this morning that quotes the VANK chairman:
VANK Chairman Park said that when Japanese figure skater Mao Asada beat Korean skating star Kim Yu-na at the Grand Prix Final last Saturday, some Korean Internet users hacked into a Japanese Web site. Some Japanese Internet users apparently thought VANK members were behind the cyber incident and decided to attack VANK's Web site in retaliation.
It was also reported on KBS (same link issue). I will continue to update if new information comes out about who was really behind any of the attacks.
End of Updated section
Gusts of Popular Feeling has pointed out that the Mao Asada - Yu-na Kim rivalry may have been behind attacks on VANK, or Voluntary Agency Network of Korea, which still appears to be down. VANK attempts to amend "distorted" images non-Koreans have of Korea, according to Wikipedia. Per this article on RJKoehler.com:
According to VANK, Korean netizens started the fight by crashing a Japanese site after Japanese figure skater Asada Mao beat Korean figure skater Kim Yun-a in the Grand Prix final in Goyang, Korea on Saturday.
Irate Japanese netizens labeled VANK as the culprit behind the attack and launched a mass "terror" (Yonhap’s word, not mine) attack on them. Japan’s largest right-wing site "2ch" is apparently spreading word on how to crash the VANK site.
The article goes on to state that the head of VANK said that Japanese "netizens" were trying to make it look like VANK was behind the attacks on Japan's site.
I knew these ladies had passionate fans, but this is another level of fandom that I am not quite accustomed to.