Seoul  - South Korean authorities issued a warning Wednesday against malicious computer software believed to have attacked about 8,000 personal computers and disabled government and private websites.

An official of South Korea's Communications Commission said the so-called DDoS (Distributed Denial of Service) attacks generate massive malicious traffic from millions of infected computers to specific sites, leading to the disablement of access for the targeted sites.

South Korean cyberpolice are investigating the hacking incident that on Tuesday night disabled or slowed the websites of banks, government agencies and portals.

The websites of the Presidential Office, the National Assembly and Defence Ministry were simultaneously bombarded with access requests, apparently caused by malicious software, denying normal access to these sites, the Communications Commission said in a statement.

"We are tracking down an IP [internet protocol] that generates the harmful traffic," Hwang Chul Jung, an official of the commission, said Wednesday at a press briefing.

Given its targeted sites, the attack might have originated in North Korea, China or another country, web security experts said.

News of the attacks led shares of some cybersecurity firms like Ahnlab Inc to rise Wednesday. (dpa)