Target has confirmed a report this morning that over 40 million credit or debit cards were involved in a major data breach, according to Reuters.

 "Target is working closely with law enforcement and financial institutions, and has identified and resolved the issue," said Chief Executive Officer Greg Steinhafel in a statement.

The breach started right around when Black Friday deals started on Nov. 27 and ended around Dec. 15 according to Steinhafel.

Secret Service is supposedly investigating the breach which involves shopper's personal credit- or debit-card information.

"The Secret Service will confirm it is investigating the incident at Target," spokesman Brian Leary said in a telephone interview Wednesday night. "We don't have any further comment because it's an ongoing investigation."

Thieves stole information stored on the magnetic stripe on the back of cards used at every Target store around the U.S., according to Krebs on Security website, who first reported the breach.

So what should you do if you've been to a Target since Nov. 27? Basically the best form of action is to wait and watch your account closely.

Yaron Samid, chief executive officer of BillGuard said not to look for big charges but for smaller ones, ranging from $1 to $1,000. Smaller charges are less likely to be noticed and disputed compared to say a charge of $10,000.

"This could be something that hits your card months from now, so you need to continue to be vigilant," says Yaron Samid, chief executive officer of BillGuard, a company that offers a free service monitoring credit and debit cards for unusual activity.

Target is based in Minneapolis and has over 1,700 stores in the U.S. and 24 in Canada.

Customers with more questions can call 866-852-8680 for more information. 

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