information in the same file by following the username with `allow'
or `deny'. Also, the user `*' can be used to set the default for
users not listed in the file. This is entirely backward compatable
with old /etc/ftpusers files.
Also, do the /etc/ftpusers and the valid login shell checks after
the password is verified, rather than before, so as not to give away
whether or not a particular user ID is present on the system.