Get a Second (or Third) E-Mail Account
Never use your real e-mail address in online chat rooms. Never use it when shopping online, and never use it to register at any website. "If you have ever done business online," says John Hambrick, an FBI supervisory special agent with the Internet Crime Complaint Center, "you have to expect that your e-mail address will be compromised; there is [then] the potential for that account to be stolen or sold."

So do what the G-man does: Establish a separate e-mail account—free on MSN's Hotmail, Yahoo!'s Mail or Google's Gmail—and use it specifically and exclusively for online purchases. The Hambrick trick should make your private accounts less vulnerable.

How to Protect Yourself
When choosing a free e-mail address for online shopping, some people opt for a pseudonym or non-identifier. As long as you have valid payment information, most retailers won't care whether or not it matches your real name. But which free service is best? "Currently, Gmail probably gets the edge," says Dr. Tygar. "It is excellent at detecting spam and phishing, though Hotmail and Yahoo are improving quickly."