Credit Cards FAQ
How do extra passwords work?
Extra passwords are a type of program offered by Vis and MasterCard to consumers and merchants that is supposed to prove extra security online. It is similar that is used to sign in for online email. With this program, you might include an extra password, known only to you and the Credit Card Company or bank when you buy from selected online merchants.
The problem is that not every e-tailer who accepts the card online participates in the program. So technically, if someone steals your number, they could still use it plenty of places online without knowing your password