I have researched this with no joy and this is my last resort. I have restricted the ftp access to an LPAR running AIX 5.3 using /etc/ftpaccess such that the user is stuck in their home directory. Not ever having tried it imagine my surprise when I connected using SFTP and the user could move to other directories. I am surprised that SFTP does not read the ftpaccess file! Anyone know of a way around this obvious security hole?
The safest bet is to build a chroot environment, this link is for sunos but i guess it should not be hard to fix.
The trick is simply to make sure all shared libraries for the few commands to be used are in the jail environment