If you have a Visa Card, MasterCard or Discover Card, you’d better keep a close eye on your bills.

Global Payments, a third-party processor of credit card payments, said Sunday that a data breach it experienced last week may have compromised about 1.5 million card numbers.

A statement from Global Payments said that while “Track 2 data may have been stolen,” cardholder names, addresses and social security numbers were not and it “believes that this incident is contained.”

Obtaining Track 2 data could allow thieves to recreate a credit card’s magnetic stripe, but provides no other information (including the often-important security code printed on the back of a card). Thus far, Global Payments hasn’t spotted any fraudulent activity stemming from the data breach, but has set up a website to keep consumers informed.

Regardless, while Global Payments continues to process Visa transactions, Visa has removed the company from a registry of partners who meet data security standards.

If you notice unauthorized charges on your cards, call your card-issuer right away. Most don’t hold their customers liable for fraudulent transactions.

[Los Angeles Times]