we already have computer system, that can't be 'infected'.
Intel and others just didn't 'Think' that far, then they designed 286-386-486 CPU's
but ... BIG secred for people like you ...
If computer system designed to separate "code" and 'data'
and "My code", "My data" and "External code/data" ...
nothing will happen.
I will Explain like you are 5th grader:
Impossible to RE-Write CD if media physically can't be RE-Written.
Impossible to RE-Write real paper book, if NO one can touch it.
You can 'Read' but can't "Touch" ...
You learn something !
people usually know "How" do job right
problem is .... $$$$$$$
Money, Lots of Money !!
We love Money !
We love Money more then we love our Mothers ...
and this is THE problem ...
it is NOT technical problem ....
Have a Nice Day.