More than 40-million people may be affected.
The stolen information included Target store brand cards and major card brands such as Visa and MasterCard.
The data breach did not affect online purchases, the company said.
Here are 7 things to know about what you should do if you suspect you might be among the victims:
1) Check your credit card statements carefully. If you discover any suspicious or unusual activity on your accounts or suspect fraud, be sure to report it immediately to your financial institutions.
2) Ask 1 of the 3 credit reporting companies to put a fraud alert on your credit report. They must tell the other 2 companies. An initial fraud alert can make it harder for an identity thief to open more accounts in your name. The alert lasts 90 days but you can renew it.
3) Order your credit reports. Identity theft victims are entitled to a free credit report from each of the 3 credit reporting companies.
4) Create an Identity Theft Report, which gives you some important rights that can help you recover from the theft. To create one, file a complaint with the FTC and print your Identity Theft Affidavit. Use that to file a police report and create your Identity Theft Report.
5) Create logs of phone calls, save documents and send letter by certified mail.
6) If you are a victim of identity theft and have created an Identity Theft Report, you may want to place an extended fraud alert or a credit freeze on your credit file. A freeze generally stops all access to your credit report, while a fraud alert permits creditors to get your report as long as they take steps to verify your identity.
7) If you have questions or concerns, contact Target directly at 866-852-8680 or visit Target's website .
You can also get more information about identity theft on the FTC's website at www.consumer.gov/idtheft, or by calling the FTC, at (877) IDTHEFT (438-4338).