What ever happened to the restricted shell flag that
allowed you to set up the CDPATH, PATH, and a couple
other things as well so that they were read only, and
access to other than the binaries that were accessible
upon login were not executable, and you couldn't change
your directory outside of what the cdpath allowed. I do
not see that in bash or ksh any more, but years ago there
was even a /bin/rsh or something that was a restricted shell
to do this. There were also other restricted binaries that
dis-allowed executing other binaries, etc.

-- 
Joseph Sarkes                   mailto:joe@mediaone.net