The scammers call you and make it seem as if they are calling from your credit card company. They give you your credit card number and all sorts of other information, making it seem like they are the real deal. Then they ask you for that 3-digit security code on the back of your card to "verify" that you are, indeed, the cardholder and have the card in your possession. Sounds legit,right?

 But it's not legit. Once they have that security code, they can now charge all sorts of purchases over the Internet.

NEVER give out any credit card information to someone who calls YOU. Tell them you will call back the company, then call the number on the back of your card and tell your credit card company about the call.

Check out these and lots of other scams on http://www.scambusters.org/ . Keep your credit card information safe!

NEVER send any information like this through email, either. I've had several clients who sent me credit card info via email, and I have to jump all over them about it. Email is SO insecure, anyone can read it. Use a secure form if you need one (I maintain one on my site, for example, just for this purpose) to send credit card info when you need to, but otherwise assume that anything you send over the Internet can be seen by anyone.