I myself programmed some malware for Linux, in FreeBASIC. It is harmless
but annoying. It has to be started manually by double-clicking the icon and you
can get rid of the effect by restarting your PC. Nothing serious. If you are
interested I will send you some versions. As for Firefox malware, I once
installed Windows live search (it can be installed in Firefox under Linux and
cannot be uninstalled) and got rid of it simply by deleting the .mozilla folder
under Slax.

What is the point of producing some when there is tons out there.

I have FF on all my MS and Linux machines and do not get malware. I use
Panda prevention on MS and nothing on Linux.