Recently there has been an increase in the level of fake emails being received by both individuals and companies requesting that your account be verified.
Ecommerce store owners using Paypal are often the target but anyone who has an online banking account is at risk. The emails look exactly as though they have been sent by the original organization. Even the reply URL (web address) looks real, but appended to it are numbers, an IP address, that sends you to theif's site where you are asked to put in your ID and Password to "verify" your account. Once you have done this it is a simple matter for the theif to empty your account.
Similarly emails porporting to be from major software vendors, most often Microsoft, appear to alert you to a virus or security hole and offer to supply the "patch" that fixes it. In reality, they will send you instead a virus or trojan horse (a program that lurks in the background to either gather information about you or allow your computer to be used for their purposes). Since you are specifically allowing the installation these programs can often even circumvent your virus protection.
The bottom line is never, never, never repond to a request that asks for you User ID and/or password. Communicate with your online institutions be independently accessing there sites by typing in the web address your self. You should also never never never open an attachment that you are not expecting even if it is from someone you know. Always know who your computer is communicating with. Good computing is like raising kids. Don't let them play with strangers ;)