Global Payments, a company that processes card transactions, confirmed late Friday that "card data may have been accessed." The company said it discovered the intrusion in early March and "promptly" notified others in the industry.
Global Payments released a statement late Sunday with more details, saying that while more than 1 million card numbers may have been compromised, cardholder names, addresses and Social Security numbers were not affected.
When a customer swipes a credit card, the data is sent to a payment processor like Global Payments, which coordinates the steps involved in authorizing the charge and submitting the transaction details to card networks like Visa and MasterCard.
For customers, the best thing to do is sit tight. If your card issuer thinks your account may have been compromised, they'll contact you -- and no matter what, you're not liable for unauthorized charges made on your account.