You really do not need such software. But for a more overall view see:
Helpful Links Regarding Malware Protection
An excellent link to read is Tom Reed's Mac Malware Guide.
Also, visit The XLab FAQs and read Detecting and avoiding malware and spyware.
See these Apple articles:
If you require anti-virus protection I recommend using ClamXav.
There have been no virus attacks that affected OS X. There are perhaps a few dozen malware programs out there, though.
It's not worth getting anti-virus, though. Mac AV is generally bloatware and most have less than stellar detection stats. Some are harmful, such as ones that delete important system files.
Just don't visit unsafe websites like sites for pirating content, and you will likely never run into any malware.