MILWAUKEE -- As many as 40 million people are at risk for identity theft after investigators said a ring of criminals hacked into the systems of several popular chain stores and stole credit and debit card numbers.

40 Million Could Be At Risk For Identity Theft

The stores involved include TJ Maxx, Boston Market, Barnes and Noble, Sports Authority, DSW Shoes, Forever 21 and others.

The hackers are accused of selling the card numbers and creating duplicate cards that were used to steal tens of thousands of dollars at a time.

The 11 suspects are from the U.S., Eastern Europe and China, according to authorities.

Government officials said this could lead to major changes.

"This is going to be a milestone moment, I think, in which people not only in the retail business, but in the systems security business, will be taking a hard look at what can be done to further strengthen network security,” said Michael Chertoff of Homeland Security.

The indictment raises questions for many consumers.

From checking your credit reports to combing through bills and bank statements, investigators said protecting yourself means staying on top of your financial records.

No one knows how many of the 41 million names and card numbers were actually used to steal credit.

Prosecutors suspect many still don't know they've been victimized.

“You should constantly monitor your credit, that's why we suggest you go and obtain the free credit report,” said Sgt. Thomas Liebenthal of the Milwaukee County Sheriff’s Department.

Consumers can get one free credit report a year from each of the three credit reporting agencies. Liebenthal suggests staggering them.

“If you get one every four months you're keeping a close eye on your actual credit rather than waiting once a year to do it,” Liebenthal said.

Prosecutors said the identity thieves engaged in what techies call war driving. They drive around looking for businesses, carry their laptops and try to log on to their wireless networks if they were unsecured.

Consumers face similar threats on their own home computers.

“If you have a wireless network within your own home and you do a lot of transactions online or banking online, your info could potentially be exposed out there if you don't take the time to secure your wireless network,” Liebenthal said.

The Milwaukee County Sheriff Department offers information on how to protect yourself or what to do if your identity is stolen at their Web site: http://www.county.milwaukee.gov/IdentityThieft9119.htm .