You don't really need any third party security software.
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 will NOT be infected by a virus, it may have other 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 seeks to offer guidance on the main security threats and how to avoid them.
More useful information can also be found here:
With the transformation to the 'cloud' and downloading from websites on the internet, the risk of contamination from viruses, worms and worse has risen.
Perhaps, but I've certainly seen worse periods in the OS X area. Clouds are relatively new, but downloading from websites goes back to the early nineties and the seventies for FTP downloads.
is there other security software that compliments it?
I'll help you with the second of Klaus1's links: Mac Malware Guide.