I found this a very interesting read – An Introduction to Linux Kernel Backdoors.
It shows some of the details that can be gleaned from reading through
the source of the Linux Kernel, and some ways that extensions could be
developed for a wide range of uses … good and bad.

I keep thinking that once more and more “un-Linux-educated” people
begin to use the operating system, they are going to fall prey to the
same types fo scams as Windows users. We already see the huge
number of people sucked into “Phishing” scams. I believe we will
see just as many people falling for entering their root passwords, etc.
on their Linux desktops.

Maybe not … but it will be interesting to see …