Lately, you may have received an email claiming to be from the IRS, telling you that you have a refund coming. You are instructed to perhaps click on a link and provide all sorts of personal information, including your social security number. Some emails might imply that you could be in some sort of trouble if you don't comply.
These emails represent what are called "phishing" scams, in which con artists send out emails that appear to be from legitimate companies or organizations in order to get your personal information, especially your SSN. With this information, they can rob your identity, opening new lines of credit and sticking you with the bill. For more information about