The last three codes of a credit card are also called CVV2 codes. The financial industry is also called securities code. Refers to the last three digits of the seven digits on the back of the credit card. As we all know, credit cards can be traded online. You only need to know the card number, expiration date and security code of the credit card to complete the payment. Some overseas websites only need to know the card number and expiration date to complete the payment. So if criminals know your credit card information, they will steal your credit card.