Lea Ann Dye, of Mount Airy, Md., has shopped online "with abandon" since 1992 but never abandons the security practices she learned in her previous work as a fraud investigator for the Air Force Office of Special Investigations.

One of her frequent checks on the credit card she uses for online shopping recently turned up an unfamiliar charge. She canceled the card. Then she received a call on her cell phone (the only number she discloses online) from a different business asking whether she’d ordered another service. Dye reviewed her file of online transactions and quickly narrowed the leak to three sites, although she was unable to determine which was responsible. After stopping the transaction, she made a report to the local police, in case thieves strike again. If you know how ID thieves operate, you should be able to take steps to protect yourself, Dye says, adding, "Identity theft is not that mysterious."