It is not CW, but CVV, which is CardVerificationValue, and Mastercard is called CardValidationCode (CVC). VISACVV and MCCVC are both 3-digit or 4-digit numbers generated from the card number, validity period and service restriction code. They are generally written in the 2-track user-defined data area of ??the card's magnetic stripe.

1: The generation methods of CVV ??and CVC are the same, but the names are different. CVV2 is a number printed in the signature area of ??a Visa/MasterCard card. It is the 3 digits after the credit card number. The last three digits we usually see on the back of credit cards are actually CVV2, not the CVV code.

One: (CardVerificationValue), which is the credit card verification value. It appears on the back of the credit card, at the top of the signature area in italics. The first four digits are the card number, and the last three digits are the verification code, which is the last three digits. Note that this verification code does not refer to the credit card password. To book a flight over the phone, you only need to enter the bank card number and the three digits behind it, as well as the expiration date of the credit card. No password is needed at all.

Two: The use of credit cards is divided into two types: "card transactions" and "offline transactions". In the former, the cardholder uses the credit card to swipe the card at POS terminals such as shopping malls and supermarkets, sign for authorization, and then complete the transaction. Offline transactions are common when cardholders book hotels, air tickets, or pay online. The merchant also provides the credit card account number and the last three digits through the POS system to complete the transaction.

Three: The last three digits are the last three digits on the back of the card. This code is generated by the encoding rules and encryption algorithm of the issuing bank. During the payment process, if the merchant provides the last three digits to the bank, the bank will by default obtain cardholder authorization for the merchant, allowing the transaction to proceed.

Four: "The last three digits are extremely critical in offline transactions, which bring convenience to cardholders and merchants. We cooperate with qualified merchants, and merchants can The cardholder freezes a portion of the funds before consumption. Only after the cardholder signs the payment can the merchant formally deduct the funds.

Five: Many domestic airlines and booking websites currently accept credit card payments. There is no need to enter a password for the service. As long as you provide the card number, validity period, verification code and other information to the website, you can pay successfully. Therefore, credit card number and other related information are particularly important, and this kind of information can easily be obtained by "interested people" who know you around. At the same time, the reporter learned that currently, all ticket booking websites are unable to verify whether the person booking the ticket is the cardholder himself. In this case, there is a possibility that "careful people" around him may take advantage of the situation and suffer a loss.