Four giant card-payment processors and large US banks that issue debit and credit cards were hit by a data-security breach after third-party services provider Global Payments Inc discovered its systems were compromised by unauthorised access.
It was not immediately clear how many cardholders became victims of the breach, which affected MasterCard Inc, Visa Inc, American Express Co and Discover Financial Services, as well as banks and other franchises that issue cards bearing their logos.
US law enforcement authorities including the Secret Service are investigating and MasterCard said it has hired an independent data-security organisation to review the incident.
The shares of Atlanta-based Global Payments, which acts as a credit-checking middleman between merchants and card processors, were halted on Friday afternoon after dropping more than 9 per cent on the news.
MasterCard shares fell 1.8 per cent to close at $420.54, Visa shares dropped 0.8 per cent to $118, American Express shares fell 0.1 per cent to $57.86, while Discover rose 1.2 per cent to $33.34.
Analysts said any financial losses from the data breach would be shouldered by merchants, card issuers and Global Payments rather than Visa or Mastercard, which operate payment networks.
Global Payments said it determined that an unauthorised entity had accessed its systems and possible customer card data in early March. Krebs on Security, a blog that first reported the incident on Friday, said accounts had been compromised for over a month, between January 21, 2012 and February 25, 2012. Global Payments is holding an investor conference call on Monday morning to discuss the issue.