According to an AFP report (which I first read at Huffington Post), MasterCard has announced that a security breach at one of its third-party processing firms has placed upwards of 40 million consumers at increased risk for credit card fraud.

One analyst quoted by CNet’s News.com said this was a big one.

“In sheer numbers, this is probably one of the largest data security breaches,” said James Van Dyke, principal analyst at Javelin Strategy & Research in Pleasanton, Calif.

Because the processor, Arizona-based CardSystems Solutions, processes cards for many firms, more than MasterCard customers are at risk. Indeed, only 13.9 million of the transaction records exposed involved MasterCard-branded cards.

As always, people need to review their credit card statements, looking carefully for anything out of the ordinary. Under U.S. federal law, your liability is capped at $50.00 for unauthorized charges, and many credit card firms will even waive the $50. And if you suspect your card may have been compromised, call the number on the back of your card and ask them for a new account number. They’ll usually get you a new card in just a few days. (And don’t forget to switch over any recurring billings you might have set up!)