The Code Red computer virus has infected around 13 thousand companies or organizations in South Korea since July 20th.
But the Information and Communication Ministry said actual damage was limited to less than 15-hundred cases.
Small companies and educational institutions were hardest hit by the so-called `worm,` which has already mutated into a second more dangerous version.
The worm attacks computers and servers running certain Microsoft software and operating systems and then spreads to other machines.
The more pernicious Code Red Two creates a path for outsiders to enter and tamper with Web sites, allowing them access to classified data such as credit card numbers.
The ministry said most organizations infected with Code Red Two have already been cured.