A card security code (CSC; also called card verification data [CVD] or a card verification The card security code is located on the back of MasterCard, Visa, Discover, card transactions instituted to reduce the incidence of credit card fraud. Description · Types of codes · Location of code · Security benefits. It is called the Card Security Code (CSC) according to Wikipedia, but has also been What is that 3-digit code on the back of the card called?. The security code written on the back of the debit/ credit cards protects the consumer in CNP (card not present) transactions, i.e. transactions made online.