Disable environment settings

[Michael ODonnell]

> Is there a way to prevent them from being able to manually
> change certain environment variables

Basically, no.  The "environment" is just a bunch of NULL
terminated strings and there's nothing sacred or special
about any of them.  The various flavors of the exec() syscall
just blindly accept and propagate whatever they're handed as
the environment by whatever process is making the syscall,
so you'd have to either change the operation of the syscall
or somehow ensure that any program that exec'd another was
willing to preserve the variables you wanted to be Read-Only...