Merchants use the American Express security code as another means to verify that the customer is in a physical possession of their credit or debit card when a payment is made online or over the phone....
Card security codes are 3- and 4-digit numbers used by the card brands to verify that a customer is in possession of her card during an e-commerce transaction....
Visa's Card Verification Value (CVV) is a 3-digit number encoded on Visa credit and debit cards, either in the card's magnetic stripe or in the chip....
CVV2 is a 3-digit code printed on the back of all valid Visa cards to help verify that a customer is in possession of the card at the time of order....
