However, like the real world, there are some dangerous neighborhoods that you should avoid. File-sharing sites that host software, music and movies for people to illegally download are a hotbed of viruses and phishing scams. Make sure you are running an updated virus protection program. It is like insurance for your computer: You may not need it all the time, but when you do, you'll be glad you have it.
Apple offers security updates through their software update program and Microsoft offers their own security suite called Security Essentials.