A 3D Secure developer is responsible for developing, testing and deploying software that enables merchants to process online payments using the 3D Secure protocol. This protocol adds an extra layer of security to online transactions, by requiring the cardholder to authenticate themselves with their bank before the transaction can be completed. The 3D Secure developer will work closely with the merchant's bank and payment processor to ensure that all aspects of the 3D Secure implementation are working correctly.