mende1 is correct: all you need is ClamXav, but here is the longer version:
There are many forms of ‘Malware’ that can affect a computer system, of which ‘a virus’ is but one type, ‘trojans’ another. Using the strict definition of a computer virus, no viruses that can attack OS X have so far been detected 'in the wild', i.e. in anything other than laboratory conditions. The same is not true of other forms of malware, such as Trojans. Whilst it is a fairly safe bet that your Mac has NOT been infected by a virus, it may have another security-related problem, but more likely a technical problem unrelated to any malware threat.
You may find this User Tip on Viruses, Trojan Detection and Removal, as well as general Internet Security and Privacy, useful:
The User Tip (which you are welcome to print out and retain for future reference) seeks to offer guidance on the main security threats and how to avoid them.
More useful information can also be found here:
I'm usually a Windows guy and I just switched to Macs. So I'm not used to Macbooks. Do I need a type of anti software for apple computers? If I do can you recommend me some or tell me how to maintain/prevent my mac from viruses, trojans, etc...
Since you are a new Mac user, I strongly suggest you do not install any anti-virus. There is, of course, a huge debate on this topic. I don't think it would be fair to ask you, as a new Mac user, to install any kind of anti-virus or "clean up" software on your system. If you aren't very careful, such software can seriously degrade your performance and reliability. Use for a while first in a factory-fresh configuration so you know how it is supposed to work. Then, later, if you add more software, you will know what the performance should be like. If you notice a change after installing some flaky 3rd party software, you will then be able to recognize it and correct it.
I purchased my first mac a couple months ago, mind you I never used anti-virus software in windows as there was no need.
I've had use for my time machine a few times now and I have performed a fresh install of mountain lion since purchase.
avoid anti virus software and just be smart with your internet usage.