What is MasterCard® SecureCode™   What is MasterCard® SecureCode™?  MasterCard SecureCode is a service from MasterCard that lets you shop online securely with your existing MasterCard Debit/Credit card.Your SecureCode enhances your existing MasterCard account by protecting you against unauthorized use of your card when shopping online at participating online retailers with the help of a personal message known only to you and your bank. Click here for FAQs