Credit card giants Visa and MasterCard were scrambling to thwart...

Credit card giants Visa and MasterCard were scrambling to thwart cyber crooks who looted a massive trove of precious account data, evidently from a payment processor in New York. Credit: Getty Images

Four giant card-payment processors and large U.S. 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 unauthorized access.

It was not immediately clear how many cardholders became victims of the breach in early March, 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.

U.S. law enforcement authorities including the Secret Service are investigating, and MasterCard said it has hired an independent data-security organization 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 percent on the news.

Banks and processors said they had not yet determined the full extent of the breach, but emphasized customers would not be held liable for any fraudulent charges that may occur.

The Global Payments breach is the latest in a string of incidents that have put the personal information of millions of cardholders at risk.

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