ClamXav not protecting against Malware and Trojans, what to do
The operating system you're using (OS X) is the best protection against Malware, Spyware and Trojans.  

Just be careful that you aren't putting in your password for anything you're not sure about.

I've run my Mac systems for many years without any anti-virus or other "protective" software.  I'm simply just careful with what I install, and ensure it comes from reputable sources.

By no means am I saying that the Mac is 100% uncompromisable.  Just saying that if you are careful, the chances of problems are minuscule and not worth the concern or system resources to keep running in the background.