Web security expert Jeremiah Grossman of WhiteHat Security identifies another point of entry: Crooks often lift Webmail account details after breaking into other sites. Many sites require your e-mail address for logging in, and many people use the same password, as well, for their log-ins to different sites.

To address this problem, take two steps: First, use a unique password for your Webmail account. Free browser tools such as can consolidate passwords. Second, when signing up for new accounts, use a "disposable" e-mail address--something , a feature in the premium Yahoo Mail Plus service ($20 per year), offers. works with any e-mail account; it's also $20 per year.