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I suggest ClamXav, that you can download at the Mac App Store. Then, run a scan with it and see if it detects any virus.
Note that most viruses are for Windows, so it's difficult that you have one for OS X. See > http://www.thesafemac.com/mmg
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.
It is unlikely you have a virus since none are known to affect OS X. Maybe you can describe exactly what the problem is that you are having.
I think I have a virus in my computer.
Don't ever jump to that conclusion on a Mac, as it's almost never the cause of any problems you will see. We can be of much greater service to you if you will thoroughly describe what you are observing and not jump to the conclusion that it's malware related.
Please modify your profile to include the version of OS X you are using as that will help us, as well.