SEOUL, South Korea — Attackers targeted about 40 South Korean government and private websites Friday, but officials reported no serious damage.
The National Cyber Security Center said there were signs of a "denial of service" attack, in which large numbers of "zombie" computers try to connect to a site at the same time in an attempt to overwhelm the server.
A top South Korean computer security company, AhnLab, said the targets included websites at South Korea's presidential office, the Foreign Ministry, the National Intelligence Service, U.S. Forces Korea and some major financial institutions.
The Korea Communications Commission said websites had reported no immediate damage.
AhnLab spokesman Park Kun-woo said the attacks were similar to ones that have targeted South Korean websites in the past and involved some of the same sites.
In 2009, some government websites in South Korea and the U.S. were paralyzed by a similar type of attack that South Korean officials believed was conducted by North Korea. But U.S. officials have largely ruled out North Korea as the origin, according to cybersecurity experts.
It was not immediately clear where Friday's attack originated.
AhnLab said a computer user discovered a bug in their system Thursday night. After analyzing it, AhnLab found malicious software designed to attack websites and told the targets in advance so that they could prepare. As a result, Park said, there had only been a brief slowing of some of the websites.
AhnLab was providing free programs to repair infected computers.
South Korean media have previously reported that North Korea runs an Internet warfare unit aimed at hacking into U.S. and South Korean military networks to gather information and disrupt service.
Park said people also point to China as the source of cyberattacks because a large amount of malware, or malicious software, originates there.
Associated Press writer Haeran Hyun contributed to this story.