3D Secure is a new technical standard developed by Visa and MasterCard to further secure customer not present (CNP) transactions over the Internet.
MasterCard brand of 3D secure is 'MasterCard SecureCode' and Visa call theirs 'Verified by Visa'. Both are available through acquirers.
Merchants should not consider 3D Secure as foolproof and should continue to use their existing anti fraud measures as well.