Name of virtual card program: Virtual Account Numbers
How it works: Citibank customers must first register with Account Online or sign on at citicards.com and click on the Virtual Accounts Numbers link in the upper right-hand corner of the Web page.
After registering, they can download software or opt for the online version of the service, which requires logging into the secure online account page of the citicards.com Web site at the time of checkout.
Those who download the software can arrange for notifications to pop up when they visit a merchant's checkout page. If they choose to launch the program, Virtual Account Numbers will then ask for their Account Online user ID and password, after which it produces a substitute card number. Shoppers then drag the number onto the merchant's checkout form, in place of their real credit card number.
Lifespan of virtual card numbers: Users get to dictate when their virtual numbers expire. They can set them to terminate within one to 12 months from the date of generation, but not past the real card's expiration date. After making these preferences, the program produces a temporary credit card number and an expiration date to use. Changing the expiration date requires creating a new virtual number. You can close a number at any time.
Where it works: Customers should not use Virtual Account Numbers when purchases require the presence of a physical credit card, such as the case for movie tickets bought online, says Rob Rosenblatt, Executive Vice President of Citi Cards.
"The Virtual Account Number technology can be used for any purchase that does not require an actual credit card plastic to be present. So, the technology can be used for online shopping as well as catalog shopping. Customers don't have to give out their real credit card number over the phone, either," Rosenblatt says.
Name of virtual card program: Secure Online Account Numbers
How it works: Discover Card customers must first register with the Account Center. Then they can choose one of two versions of the service: PC users can download it to their desktop; PC and Mac users can access it online by signing in on the Secure Online Account Numbers launch page.
The downloaded version helps customers fill out checkout forms and pops up automatically when a customer goes to a merchant's checkout page.
Users can access the online version from any computer but cannot use it to fill out forms. Nor does it pop up automatically. Shoppers have to go to the Discover Card Web site and log in with their Account Center user ID and password each time they want to use a secure online account number at checkout.
Both versions produce a substitute credit card number for use in online shopping and telephone orders.
Lifespan of virtual card number: Expires when customer's Discover Card expires.
Where it works: Anywhere that Discover Card is accepted, including online retailers and telephone orders. Customers can also use the substitute credit card number for online bill payment. However, the virtual card number shouldn't be used in cases where the physical card is needed to complete a purchase.
Bankrate editorial assistant Leslie Hunt contributed to this story.