Details of 573,928 credit and debit cards may have been stolen by criminals who planted code on servers supporting e-commerce merchant Web sites hosted by Network Solutions.
The company says the unauthorised code was on its servers from 12 March to 8 June and may have been used to transfer data on transactions Network Solutions processed for about 4343 merchant Web sites.
Network Solutions says the code has been removed and it has no reason to believe card account information has been misused. The firm is now working with law enforcement officials.
The company is notifying affected merchants and offering to help them inform cardholders. Affected cardholders are also being offered one year of free credit monitoring from TransUnion.