A major security breach at Global Payments, which does transaction processing for Visa and MasterCard, has exposed the credit card data of millions of customers to potential theft.

The breach, which was first reported in a blog at Krebs On Security, has been acknowledged by Global Payments, though neither the exact origin of the breach nor the scope of the compromise have been revealed.

In a published statement, Global Payments Chairman and CEO Paul Garcia said the company found the compromise itself in early March.

"Global Payments Inc., a leader in payment processing services, announced it identified and self-reported unauthorized access into a portion of its processing system," the statement says.

"In early March 2012, the company determined card data may have been accessed. It immediately engaged external experts in information technology forensics and contacted federal law enforcement," the statement says. "The company promptly notified appropriate industry parties to allow them to minimize potential cardholder impact. The company is continuing its investigation into this matter.

"It is reassuring that our security processes detected an intrusion," Garcia says in the statement. "It is crucial to understand that this incident does not involve our merchants or their relationships with their customers."

Some experts estimated that the compromise may be in the range of 1 million to 3 million accounts. This is the second time that Global Payments has been breached in the last year, according to news reports.

Have a comment on this story? Please click "Comment" below. If you'd like to contact Dark Reading's editors directly, send us a message.