Ecommerce applications can be secured in many different ways from simple use of password to use of smart card.
This is the most commonly used technique to protect applications. Username/password is required to access an application. Different users may have access to different portions of the same application.
An application is programmed or configured to accept users from a set of particular IP addresses.
A pair of public/private keys are used to protect an application.
Each user of an application posses a smart card (the size of a credit card). The smart card displays different password (random numbers) every a few seconds. The time-sensitive password provides much stronger security to an application than simple password protection does.
Network Security for Ecommerce Systems
Physical Security for Ecommerce Systems