The security code of Bank of China Great Wall Credit Card Mastercard is printed on the back of the credit card, in the signature area.

Credit card security code is a security code for credit cards when conducting online or telephone transactions. It is usually a 3 or 4-digit number printed on the credit card, and the location of the printing will vary on different types of cards. It is often used to prevent credit card fraud by verifying that the payer owned the credit card at the time of the transaction.