Believe it or not, even a savvy person like me is subject to fraud once in a while. Perusing our most recent credit card bill, I came across three charges that were clearly not ours - small charges made at gas stations in another state. When we called the credit card company, they determined that our card had been duplicated, since the charges had been swiped through a card reader. Apparently, at some point recently our credit card data must have been double-swiped through a magnetic card reader and then transferred to a duplicated card.
The duped card was then used for small-ticket purchases at innocuous locations intended to evade the bank's fraud detection algorithms. The pattern is the fraudsters pilot a couple of small charges, and if the account holder doesn't shut off the card, much larger charges are made.
I'm now part of the group of persons defrauded in this type of scam, but the fraud group at Chase caught it after 3 $20 transactions.