Is the restricted shell really secure?

[John Bruner]

You should be able to keep a restricted account from wandering afield
via ".." by making the parent directory non-executable. I.e. make the
home directory for the restricted account "foo" be "/mnt/locked/foo"
(replace "/mnt" with whatever top-level directory you plan to use)
where "/mnt/locked" is owned by root and is mode 700.

This assumes, of course, that the restricted account isn't running
under user-id 0 :-)
-- 
  John Bruner (S-1 Project, Lawrence Livermore National Laboratory)
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