Sometimes being in the minority has its benefits!
The threat to Macs from viruses and trojans ('malware') has always been minimal - but they are out there, and they will come soon enough, so it doesn't pay to become too complacent. Even Apple recommends you invest.
The majority of malware infects and affects computers running Microsoft Windows and its products, and it is more the fact that you as a Mac user may inadvertently pass on infected files (like Word or Excel documents, for example) that will subsequently infect an unprotected or unpatched Windows PC.
Rule #1: Do not install software from untrusted sources, especially if that software comes as an installer package and requests your administrator’s password!
It is also extremely likely nowadays that if you attempt to email an infected document that it will be bounced back to you, having been detected by the recipient's mail server as infected, thus rendering them incapable of receiving the file - which can be a right PITA*.
You should install Apple System and Security Updates as they become available, and be sure to download the latest antivirus definition updates - your protection is only as good as your last update!
> Identifying and removing the OSX.RSPlug.A Trojan Horse malware: Macworld tutorial
Mac AntiVirus Software:
Virex (now McAfee VirusScan v8.x)
• Note: Virex 7.5.x is NOT compatible with Tiger 10.4 (but v7.2.1 still seems to be on PPC based Mac, and uses the same latest definitions). Virex 7.7 is listed as 10.2.9 or later, 10.3.3 or later and 10.4 or later compatible, PPC only. Virex 8.6 is listed as 10.4.6 or later and 10.5 or later compatible, Intel and PPC.
• Virex 7 Definitions (DAT) update
• To automatically eUpdate Virex 7.2.1 DAT via FTP:
- open the Virex preferences, go to the bottom of the page under Virus Update, check the box Customize my eUpdate server settings and click the radio button Server Settings.
- select Type as FTP from the pop-up menu
- set Server URL: ftp.nai.com; Port: 21; Username: anonymous; Password: leave blank; Account: leave blank; Directory: /virusdefs/mac/virex7/
- be sure to also check the Check for new virus definitions at Launch box.
Norton AntiVirus
• Symantec NAV Mac virus definitions : for NAV Mac versions 7, 8, 9 and 10
• Note: NAV Mac 9.x and earlier are NOT compatible with mac OS X 10.4 or greater.
• Note: Software updates via LiveUpdate only. Annual subscription.
Other Mac Antivirus Options
ClamXav : a free, open-source virus detection (but not cleaning yet) application with free daily updates.
Intego VirusBarrier X4 : Definitions and updates only available through subscription.
(*Netspeak for significant inconvenience)