Afraid to shop online because identity thieves might steal your credit card number? Last year nine million people were victims of identity theft, with losses to victims and businesses exceeding $50 billion. Almost one-third was due to credit-card fraud. Here's how to protect yourself with something simple and easy to obtain — a temporary credit card number. Some banks and financial institutions, such as Citibank and Discover Card, offer temporary one-time, one-use credit card numbers that are designated for a specific merchant and for a specific purchase. They're in no way linked to you or to your real account with that bank or financial institution. Check to see if your cards offer this service. If not, find out who does.