A credit card security code provides protection against fraud in online and over-the-phone transactions.

These three- or four-digit numbers provide an additional layer of security. Here is what you need to know about credit card security codes and how to find them by issuer.

What Other Information Is Needed Besides a Credit Card Security Code? More people are shopping online and using their credit and debit cards to pay for purchases.

A card security code is a three- or four-digit number on the back of credit and debit cards that ensures the authenticity of transactions when a physical card is not presented at the point of sale.