When it released Mac OS X, Apple became the largest vendor of a Unix-based operating system. Unix is a highly popular operating system and is much more well known by hackers good and bad than earlier versions of the Mac OS, which were generally considered much less interesting to serious hackers, virus writers, and other digital creeps. Well, six years into the OS X journey, we've yet to see a serious virus or spyware threat, which means that if you're not using an antivirus solution, that's not as bad as, say, not backing up.
However, if you own an Intel Mac and you run (or plan to run) Windows via Apple Boot Camp, Parallels Desktop for Mac, or VMware Fusion, you should get some virus protection ASAP. Intego's Internet Security Barrier X4 Anti Spam Edition Dual Protection ($99.95) is a complete security suite that includes firewall, antivirus, and antispam features - the "Dual Protection" part of its name means it protects against viruses when you're running Windows on a Mac, too. As far as freeware protection goes, there is a program known as Climax. Since we don't regularly review security software, however, and since Climax is freeware, we haven't checked it out and can't vouch for it (or say anything against it).
More important than virus protection is to practice safe computing: Don't leave FTP or other services open, especially when you're not doing your online banking while surfing a public Wi-Fi hotspot! (Seriously, you shouldn't transmit any sensitive info online when connected to a public Wi-Fi network unless you're using a Virtual Private Network, or VPN, connection. For more, read 11 Foolproof Ways to Make Your Mac Secure.) And whatever you do, don't give your credit-card information to that Nigerian fellow who needs a couple thousand bucks to claim his daddy-the-dead-dignitary's billions.
Besides rooting out viruses and spyware, Intego's software also helps you can spam.
