Harden-clients gives the administrator an easy way to avoid installing clients that are insecure in some sense. it conflicts with: clients that need to send passwords in plaintext, and packages that can give someone access to the local host without permission.
note! this package will not make your system uncrackable, and it is not intended to do so. making your system secure involves a lot more than just installing a package.
for more information on how to secure your system see: http://www.debian.org/doc/manuals/securing-debian-howto/