Ensure root is the owner of /etc/grub.conf then

chmod 700 grub.conf

This makes root the only person who can rw to it.

This should be set up at install time

Edit the file /etc/sysconfig/init. Add or correct the setting:

PROMPT=no

While editing this file also turn off graphical boot

GRAPHICAL=no

To disable core dumps for all users, add or correct the following line in /etc/security/limits.conf

* hard core 0

In addition, to ensure that core dumps can never be made by setuid programs, edit /etc/sysctl.conf and add or correct the line:

fs.suid_dumpable = 0