"I am aware that linux operating systems are immune to windows Viruses and spyware,but it is only a matter of time when linux operating systems become popular"
First, implementation doesnt matter, logic does. Still there are, and there will be NO viruses for linux.

Linux is used as a Web server OS on 40% of machines.
Goverment,corporation and military servers operate linux.
Reasons linux is a bad platform for viruses:
- Totally and always Open Source.
- Possibility to recompile everything from scratch on own platform.
- Protected repositories.
- Time-between-patches.
- No "standart" version for any program. Amount of patches.
- Possibility for manual code modification.
- No "standart distribution" or "standart" version.
- Fragility of binary format(ELF).
- UNIX class security from start.
- AppArmor/SELinux extensions.

The first and only thing is to understand ideology and security model of Linux and use it.
Antivirus is only needed to filter Win* traffic and Win* infection.

Check this:

http://www.whylinuxisbetter.net/items/viruses/index.php?lang