If people tell you that Mac computers are virus free, do not believe them. They are stupid. There are actually people who still say things like that until now. While Microsoft Windows bears the brunt of all virus, malware and spyware out there it does not mean that Mac OS-run computers are safe.
The virus may not run in Mac OS but they are just waiting there idling, waiting for some USB to be inserted and plugged in some Windows-run computer. There are also Mac OS viruses but they are not that many. I believe in time they will number a lot when Apple becomes more arrogant.
There is a free antivirus software for Mac OS called iAntiVirus. The user interface is pretty simple and self explanatory you won’t have a problem using it. The iAntiVirus database has been designed from the ground up to detect and remove Mac specific threats.
This enables a high level of protection whilst keeping memory footprint and resource usage at a minimum. The iAntiVirus database is not cluttered with signatures for Windows specific threats which your Mac is immune against.
It features a variety of scan options, real time protection, quarantine and smart updates to update your virus signature list. As I said, it’s free! So it’s what makes it appealing ;).