You appear to be assuming
that Linux runs the same way as Windows with the same vulnerabilities. First, Linux even requires the Admin to enter a password to make changes - unlike Windows (at least through XP - and even in Win. 7 if you click on "Continue" logged in Admin mode). Second, Linux is built on the same model OS as Unix - Windows is not - it was "hacked" together from a CP/M clone which, back in those days, function was to make the micro H/W work and security was not an issue back then. Unix was built and evolved in a "mainframe world" with different considerations. Inherently, Unix (thus Linux) is a much more secure system. BTW, if you get into the IBM mainframe world, when was the last time you ever heard of one of their systems being hacked? Especially, their zVM system? There are ways, of course, but it would take "cooperation" of the user installation by adding "hooks" to allow for outside users to hack into it and, even then, it would be near impossible.
Remember, CP/M, its clones and many other micro PC OSes back in the early days were essentially "hobbyist" - just make the H/W work so one could write their Basic and Assembler language programs to do some of the "neat things" PCs can do. I suspect if IBM had developed the PC code "in-house", the OS (and inherent security) would have been considerably different. Even OS/2 was jointly developed in the early years - BTW, OS/2 is still in use today - especially in the Banking industry.
And as D.E. points out, you have A/V S/W available as well as Firewall protection.
