The following is from the Trend Micro site. I am not endorsing their product(s) and I'm not getting paid to say this but... I use them and am very happy with the results. Please read the below and protect yourself.

Every year more people file their annual taxes online—and every year scammers find new ways to try to steal millions of Americans’ personal information. If there’s one thing you can do to protect yourself online, it’s this: do not respond to emails that appear to come from the IRS offering you a refund.

The Internal Revenue Service will never, ever send you an unsolicited email about your finances. Never. Take those weird emails with subject lines like “YOU HAVE A REFUND” and junk them.

A few other things you can do to thwart the scammers:
§ Do not file your taxes from an Internet café. Even if you’re on your own computer, many publicly available wireless networks are vulnerable to intrusion because they aren’t encrypted. Additionally, crooks have been known to set up public wireless networks with names that sound like legitimate hosts in order lure people into using them. Be safe and file your taxes from a secure, encrypted connection.
§ If you file your taxes through the mail, drop them off at the post office. Remember that identity thieves are always happy to follow the path of least resistance—and it’s the easiest thing in the world to snag somebody’s tax return out of their mailbox. Submitting your forms at the post office adds one layer of security in the path from you to the IRS.
§ Just as the IRS will not email you about your tax return, they will never call you to ask you for personal information so that you can get your refund faster. Do not give out your personal information over the phone.
§ If you’re filing online, chances are you might have some of your important tax information stored on your computer in Quicken files, Excel spreadsheets, or other formats. Make sure your firewall, antivirus, and anti-spyware programs are all up to date to prevent intrusions that could result in this information being accessed and stolen.