What is 3D Secure?
Depending on the card type, this security check is called “MasterCard SecureCode” or “Verified by Visa”.
How does it work?
It’s quite straight forward. When you're making a purchase with your card, a pop-up window may appear from your bank. You'll be asked to enter a pre-registered password to confirm that you're the cardholder, before completing the payment. You may first be asked to set up your card for 3D Secure and create a password if you haven’t already done so.
Is this password the same as my PayPal password?
More information about 3D Secure.