In August, an alert shopper noticed something a little strange about an ATM near the popular outdoor Portland Saturday Market in Portland, Ore. A thief had attached a skimmer -- a device that "skims" your debit or credit card number for fraudulent purposes -- to the ATM. The shopper alerted market security, but no one knows how long the skimmer was attached or how many credit card numbers were taken.

The idea of debit or credit card fraud can strike cold fear into even the most tech-savvy consumer. Once someone possesses your credit card or debit card number, you're looking at a passel of phone calls to your card issuer, filling out police reports and possibly a delay before the issuer credits your account.

Review these mistakes to avoid becoming a victim of debit or credit card fraud.