It took a long time to figure out how our credit card number was stolen. Almost a year after it happened, we got a letter from an online store thst DH buys bike equipment from. They said that someone had hacked onto their system and was getting their customers information.
So now we use virtual online numbers through Citibank. It's like a one use number, so if someone tries to use it again, it won't work and a red flag goes up. I love it!