Several dozen cases of computer problems have been reported since Saturday after users logged onto an Internet auction site that had earlier been hacked, the Information-technology Promotion Agency said Tuesday.

The affiliate of the Ministry of Economy, Trade and Industry said most cases involved users having problems running software and not being able to start up their computers.

According to the IPA, hackers installed a program on the auction site that automatically alters the set-up data of some software.

The program has since been removed, but the IPA is calling for computer users to take preventative measures after learning that similar problems were reported on a different Web site.