Location: The credit card security code is the last three digits in the signature area on the back of the card as seen below. If using American Express, the security code will be four digits on the front of your card.
Purpose: The security code has been added by the credit card companies to help prevent fraud. Because the
security code is neither stored on the magnetic strip nor embossed on the front of the card it is more difficult for your card to be used for fraudulent purposes.