CCV is a new authentication scheme established by credit card companies to further efforts towards reducing fraud for internet transactions. It consists of requiring a card holder to enter the CCV number in at transaction time to verify that the card is on hand.
Visa & MasterCard: This number is printed on your cards in the signature area of the back of the card. (It is the last 3 digits AFTER the credit card number in the signature area of the card).
American Express: This number is printed on the front of your card. (It is the last 4 digits).