A lot of payment providers have implemented 3D Secure as a way of reducing fraud.  This system sends customers off to a 3rd party service after entering their card details, where they are presented with a form that requests their password.  Upon entering their password successfully, they are returned to the site and payment is taken.

Bypassing 3D secure

In order to allow telephone orders, 3D secure is bypassed for all admins.  Once you login to Aurora, a cookie is set called "ac_stats_no"  for a duration of 365 days.  This means even if you have logged out of Aurora, this cookie will remain and you will bypass 3D secure.  If you need to test 3D secure, you will need to delete the "ac_stats_no" cookie for the domain you are on.  In specific browsers, such as Firefox, you can delete individual cookies, whereas other browsers only allow you to delete all the cookies for an individual domain. Once you have done this, 3D secure will be enabled again.