A core issue associated with using the remote interface is security. The collection and storage of payment information, such as card numbers and cardholder names must take place in a secure environment. Even if you do not store the card details, handling the card details (such as allowing customers to enter them within your systems and then sending those to the gateway) will require PCI DSS certification.
Payment Card Industry Data Security Standard (PCI DSS)
PCI DSS is a global Card Scheme initiative that aims to ensure that every entity that handles, stores or processes cardholder data does so in a secure manner. MasterCard and Visa have combined their own security standards for cardholder data creating an aligned program, which is now endorsed by American Express, JCB and Diners. Much of PCI DSS relates to the technology involved in capturing and processing card data and this is particularly relevant to those merchants who process and capture cardholder data on their own systems rather than those who use the Hosted Payment Pages.
For more information, please refer to PCI DSS and to the PCI Security Standards Council at https://www.pcisecuritystandards.org. If you want any help to gain compliance this site also lists PCI approved Quality Security Assessors (QSAʹs) who can provide technical advice.