An army of "zombie computers" infected by a hackers’ program paralyzed major government, bank and newspaper websites in South Korea in cyber attacks that officials here said on Wednesday were apparently linked to similar attacks in the United States.
Access to 25 Web sites — including those of the presidential Blue House, the Defense Ministry, the National Assembly, Shinhan Bank, the mass-circulation daily newspaper Chosun and the top Internet portal Naver.com — have crashed or slowed down to a crawl since Tuesday evening, officials at the government’s Korea Information Security Agency said.
On Wednesday, some of the sites regained service but others remained unstable or inaccessible, as floods of infected computers still tried to connect to the sites the same time, overloading and that paralyzing servers, they said.
In the United States, 14 major Web sites — including those of the White House, the State Department and the New York Stock Exchange — came under similar attacks, according to anti-cyber terrorism police officers in Seoul, who suspected a link between the two waves of attacks.
The Associated Press reported that a widespread and unusually resilient computer attack that began July 4 knocked out the Web sites of several government agencies, including some that are responsible for fighting cyber crime.
The Treasury Department, Secret Service, Federal Trade Commission and Transportation Department Web sites were all down at varying points over the holiday weekend and into this week, the news agency reported, citing officials inside and outside the U.S. government. Some of the sites were still experiencing problems Tuesday evening.
In South Korea, the Blue House reported no data loss or other damage except disrupted access. The Defense Ministry and banks attacked also reported no immediate loss of security data or financial damage.
"The traffic to our site surged nine times of the normal level," the Blue House said in a statement. "Computer users in some regions still suffer slow or no access at all to our site."
Hwang Cheol-jeung, a senior official at the government’s Korea Communications Commission, said the attacks were launched by zombie computers infected by a well-known "distributed denial of service," or DDoS, hackers’ program. About 18,000 computers are believed infected in South Korea.
"The infected computers are still attacking and their number is not decreasing," Mr. Hwang told reporters in a briefing. The government was urging users to upgrade their computers’ antivirus software to fight the virus.
DDoS attacks are relatively common. But they can create a serious nuisance if hackers commandeer thousands of computers.
The South Korean news agency Yonhap said the police
have traced a possible starting point for the attack back to members of a small cable TV Web site in Seoul. But officials said that doesn’t mean it originated there.
Mr. Hwang said South Korean authorities suspected that the attack may have been caused by a new variant of DDoS.