A computer virus launched an apparent denial of service attack on 40 Web sites in South Korea on March 4, including the sites of the presidential Blue House, the Foreign Ministry, and several U.S. military sites. The virus was discovered the day prior to the attack by AhnLab, a Seoul-based Internet security firm.

Although AhnLab quickly distributed an antivirus solution to protect against the virus, it was not able to prevent the attack from being carried out. A spokesman for AhnLab says that the attack was similar to one that took place in 2009, though the most recent attack was not as serious.

An official in the South Korean government, meanwhile, says the attack did not cause any major damage to the computer systems at the Blue House. It remains unclear who was responsible for the attack.