Helpful Links Regarding Flashback Trojan
Visit Thomas Reed's site for insight and help: Mac Malware Guide
A Google search can reveal a variety of alternatives on how the remove the trojan should your computer get infected. This can get you started. However, be careful about what you do as new variants of the malware circumvent the efforts of earlier tools.
Also see Apple's article About Flashback malware.
Apple has released Java updates for Snow Leopard and Lion users:
Java for OS X Lion 2012-003; available only for users of Lion with Java installed.
Java for Mac OS X 10.6 Update 8; available only for users of Snow Leopard.
Flashback malware removal tool; available only for users of Lion without Java installed.
Install whichever shows up in Software Update. It removes the malware (if present), updates Java (if present) and tightens up Java settings for the future. You may download from Apple's web site instead of using Software Update, but it's important to know which one to get, because the other two won't work for you.
For the truly paranoid see 10 Simple Tips for Boosting The Security Of Your Mac.
Since you're new here, I'll try to explain the best way I can. The Flashback malware which has hit 600,000 Macs last week, is a wake up call to all Mac users. Since Macs have started gaining market share, they're now a target for such malware. Another thing to note is that there's no such thing as 100% secure. There's always going to be some sort of vulnerablility that Mac OS X will have that can be exploited. There is a free anti-virus product that you can download and install on your Mac. Sophos (www.sophos.com) has an free anti-virus product that you can donwload. It's called Sophos Anti-Virus Home Edition for Mac. Once installed, you'll be protected. I highly recommend this program, since it's updated very frequently. Apple has been slow when it comes to patching, and the lastest malware attack that affected those Macs proves the point. All Mac users are no longer immune, so be very vigilant in regards to security. Contrary to what people has said, now there's a good reason to have an anti-virus product installed on your Mac. Please take my advise and install the anti-virus product I mentioned. I've been running Sophos Anti-Virus on my Mac for over a year, and I haven't had any infections.