Carrier,
That article isn't about anti-malware for iMacs. Interesting subject but probably better discussed in Jet Blast.
YellowTriumph look into Macro Viruses for MS Office products.
In today's iteration of the Mac OS, there has never been a (self-propagating) virus. Trojans, which attempt to fool the user into loading the malware, do exist and you need to be careful.
Check your firewall settings (lots of good advice on the Internet, and on Apple support pages).
Create a User ID with no administrator privileges and use that for day-to-day computing. Be suspicious if/when you are asked to enter your administrators password. In the system preferences under privacy there are some settings that shoul be set tightly, for example to allow downloads only from Apple and known companies. An administrator can always override these settings, but it does make one think "should I really be doing this"?
Join the Apple Support Communities.
https://discussions.apple.com/welcome Which is maintained by Apple, but it's Apple users who contribute to the discussions. You can learn a lot here.