S.Korea attacked by reactivated computer virus

South Korean government and private websites have come under cyber-attack a year after a major attack briefly crippled sites domestically and in the United States, officials said Thursday.

Five websites including those of the presidential Blue House and the foreign ministry were attacked Wednesday but little damage was done, the Korea Communications Commission (KCC) said.

On July 7, 2009, the so-called distributed denial-of-service (DDoS) attacks shut down 25 Internet sites for hours - 11 in South Korea and 14 in the United States.

"The DDos attacks resumed exactly a year later as some contaminated PCs were left untreated," the KCC said in a statement.

"However, no obstacles were created in getting access to those sites as the traffic from zombie computers was negligible," it said, referring to computers unknowingly contaminated with a virus.

The commission told Internet service providers to urge those using contaminated computers to erase the virus.

Police said 462 computers were used in Wednesday's attacks, a tiny figure in comparison to last year's that mobilized 270,000 computers. But they warned there could be follow-up attacks on a second and third day.

South Korea's spy chief has reportedly blamed North Korea's telecommunications ministry for last year's attacks, although US officials reached no conclusion.