3D Secure is a technical standard created by Visa and MasterCard to further secure CNP (Card-holder Not Present) transactions over the Internet.
MasterCard brands their system as 'MasterCard SecureCode' and Visa call theirs 'Visa Secure'.
3D Secure protects a buyer's credit card against unauthorised use when shopping online. This simple service enables buyers to validate transactions you make over the internet by requesting a personal code (usually sent to your cell phone or email address as a one time PIN). It helps protect against fraudulent use by unauthorised individuals.