Sometime Today, DJ cobbled together some glyphs to say:
Plus, the source code for Linux kernel and GNU apps have been around for atleast a decade. When you have the source code it's easier to write exploits, virii but it just doesn't seem so with GNU/Linux ;)
It is only easier to write exploits if exploits are possible. Remember that there are many many more good people in the world than there are bad people, and many of these good people actually do code reviews and warn authors about potential security flaws in their code. Because of this, security flaws in opensource code (which do exist) get fixed sooner than anyone has the time to exploit it.