D-Day was July 7. Around 7 p.m., the number of visitors to 12 major local websites such as Cheong Wa Dae, the National Assembly, the Defense Ministry, and the Chosun Ilbo suddenly surged. As the number of computers attempting connections reached the tens of thousands, websites went down because they could not cope with the enormous traffic. At the same time, access to 14 major U.S. websites such as the White House and the State Department also became paralyzed.

The so-called "distributed denial of service attack" had been launched automatically through ordinary web users' personal computers infected with a virus.

The Korea Information Security Agency believes more than 18,000 personal computers in the country are infected by the DDoS virus. To prevent other users' computers from being used as a source of such DDoS attacks, domestic computer security firms Ahnlab and Hauri have made a vaccine available for download.