A breach at Network Solutions has exposed details for more than 500,000 credit and debit cards after hackers penetrated a system it used to deliver e-commerce services and planted software that diverted transactions to a rogue server, the hosting company said late Friday.

The unauthorized software was in place from March 12 to June 8 and affected transactions Network Solutions processed on behalf of 4,343 merchant websites that mostly belonged to small businesses, spokeswoman Susan Wade said. While the company discovered the software in early June, it waited until the close of business Friday to disclose the breach. Wade said it took until July 13 for forensics investigators to crack the code and understand how it worked.

"We have been working around the clock to get this announcement ready," she told The Register. "We're really making an effort to be forthcoming. This is really tough on our customers that were impacted, and we feel very badly."

Network Solutions is working with undisclosed law enforcement agencies to figure out who is responsible for the breach and how it happened. In all details for 573,928 card holders may have been siphoned in the attack, which affected different merchant websites at different times over the three-month period that the rogue software was in place.

So far, there are no indications that any of the exposed cards have been misused.

Network Solutions has offered to foot the bill for notifying affected cardholders so those costs don't have to be born by the merchants who used the company's e-commerce service. In Most US states, laws require such notices to be made when breaches are discovered that expose credit card information.

The company is also making 12 months of fraud-monitoring services available free of charge to cardholders whose information was exposed. Affected merchants and cardholders can enroll by visiting this site, which walks them through the process. ®