Target said Thursday that about 40 million credit and debit card accounts may be affected by a security breach over 19 days this holiday shopping season, including over the Black Friday weekend. If you think you might be a victim of the data breach there are several things you can do to protect yourself. The safest thing, experts says, is to cancel your credit or debit card and get a new number. "If it was my debit card, I would probably cancel it," said one fraud analyst. "I don't like anyone going into my bank account." If you decide to keep the same card, check it for suspicious charges at least once a month. Also, if you swipe your debit card at the checkout, always make sure to do it as "credit" rather than "debit." Though no reports indicate PINs were stolen during this breach, if they were, a thief could copy your debit card onto a new piece of plastic and use it at any ATM in the world. Click through for more on what you should do if you think you might be a victim.