This code is generated by the coding rules and encryption algorithm of the issuing bank. In the payment process, if the merchant provides the last three codes to the bank, the bank will obtain the authorization of the cardholder to the merchant by default, thus allowing the transaction.
The use of credit cards can be divided into "on-card transactions" and "off-line transactions". In the former, the cardholder swipes the card at POS terminals such as shopping malls and supermarkets, signs the authorization, and then completes 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 codes through the POS system to complete the transaction.
Extended data
Techniques for preventing cvv code leakage;
1. When spending by credit card, don't let the bank card leave sight. Pay attention to the number of times the cashier swipes the card to avoid mistakes and excessive swiping.
2. When entering the password, you should use your body or the other hand to block the operation gesture as much as possible to prevent being peeked.
When you get the receipt and card returned by the cashier, you should carefully check whether the amount on the receipt is correct and whether the card is really mine.
4. After receiving the bank card statement, you should check the use of the card in time. If in doubt, you should call the bank's customer service hotline in time.
Baidu encyclopedia -cvv