A credit card's security code, also known as CVC or CVV, is an important set of numbers located in key locations on the card and is used to enhance the security of online and phone transactions. It is usually located in the last three digits of the signature area, and the location is different for different card types: VISA card: next to the last 4 digits of the card number, there are 3 digits. MasterCard: There are also 3 digits next to the last 4 digits of the card number. Discovery Card: The security code is also printed in the signature field, ***3 digits. American Express Card: Located on the front of the credit card, above the card number, there is a 4-digit number. UnionPay card: The location is the same as that of VISA and MasterCard, that is, there are 3 digits after the last 4 digits of the card number. JCB card: The security code is located after the last 4 digits of the card number, and there are also 3 digits.

The generation of the security code is based on a complex encryption process of card information. Only the issuing bank and the cardholder know this number. This number plays a key role in validating transactions, ensuring only the cardholder completes the transaction, thereby reducing the risk of fraud. When making any form of credit card transaction, remember to check and enter the correct security code to ensure the security of the transaction.