The temporary number, rather than the real credit card number, is given to the merchant and the order is processed in the normal way. As soon as the transaction is completed the number expires, and the cardholder will need to apply for another one next time he buys on-line. There are other ways merchants can shore up defenses. US-based companies such as Clear Commerce, CyberSource and HNC Software offer services that compare a shopper's email address with their Internet protocol address and shipping address. These screening systems work because they build up a database with transaction records from all on-line merchants worldwide who use the software.
Software companies use the records to track recurring patterns of fraudulent transactions.
For instance, an order should be examined if the same card has been used in a rush of large-sum transactions. But there's a limit to what such software can do. More than a thousand portals provide anonymous, free email accounts. CyberSource executives admit it is impossible to keep up. Herman Cheng, regional solution integration director of Web Connect, an Internet consultancy, advises clients to adopt fraud detection software - but warns that it is only as good as merchants want it to be.