As there are no viruses (there are other forms of malware though) an antivirus apps on a Mac is a complete waste. The malware I am referring to has be downloaded and installed by the user so using bit of common sense one can easily avoid these. In 15+ years of Mac use the only protection I have is keeping Mac OS up-to-date and otherwise leaving it alone. In 15 years I have had zero malware, zero issues and my Macs have ALWAYS been stable and fast.
I'd recommend that your read https://discussions.apple.com/docs/DOC-8071 and to avoid malware follow these simple rules:
- Never download from a site you do not know and trust.
- Do not fall for scams as discussed in the link above.
- Never use a torrent to download software that you did not pay for.
I think you will find most experienced users on these forums agree with my strategy.