The security code of 1.VISA card is called CVV2 (card verification value 2), which has 3 digits and is printed on the last 4 digits of the card number on the back of the credit card.

2. The security code of 2.MarsterCard is called CVC2 (Card Verification Code 2), which has 3 digits and is printed on the last 4 digits of the card number on the back of the credit card. In online transactions, we are often asked to fill in the last three digits of the signature column on the back of the credit card, that is, the credit card security codes CVC2 and CVC2.

Extended data credit card security code is the security code of credit card when conducting network or telephone transactions. Generally, it is a 3-digit or 4-digit number printed on a credit card, and the printing position of different types of cards will be different. It is usually used to prove that the payer has a credit card at the time of transaction, thus preventing credit card fraud.

Refer to Baidu Encyclopedia-Credit Card Security Code