This probably depends on the regulation of the country. For example, in India, by LAW, all domestic online transactions go through two-factor authentication. F

This probably depends on the regulation of the country. For example, in India, by LAW, all domestic online transactions go through two-factor authentication. For one of my cards, I need to enter a secondary password while for another I need to enter a pin texted to my mobile. The second option is a hassle though, especially when I am travelling abroad and my standard mobile number is not functional. For international transactions, this does not apply and the card details are enough for the transaction to go through. I guess there is no standard agreement between countries which Visa, MasterCard or Amex can implement (these are the only payment networks I use).