In order to process payments with Visa and Mastercard credit cards, we now need an additional element : the CVV2 or CVC2 security code. This 3 digit code is found on the back of your credit card.

What is CVV2 or CVC2?
The CVV2/CVC2 is a three-digit security code that is printed on the back of credit cards. The number appears in reverse italic at the top of the signature panel at the end (see sample). This program helps validate that a genuine card is being used during a transaction. All MasterCard cards, both credit and debit, were required to contain CVC2 by January 1, 1997; all Visa cards must contain CVV2 by January 1, 2001. Even if a criminal steals a valid account number, They cannot compute the CVV2 numbers since they do not know the mathematical algorithm logic.

Where is CVV2 Located?
The CVV2 three-digit value is printed on the signature panel on the back of Visa cards immediately following the Visa card account number. Click for illustrations showing the location of this code on a Mastercard and on a Visa.

I found a number on the back of my card, but it has more than 3 digits
We only need the last 3 digits of this number (the other are just a repetition of your credit card number).