initial security

hi
i've got a bare bones linux system up and running.
but zero security on it.
i dont want to change it since i've hacked the kernel and got a bunch  of stuf fon it taht i like
and for reasons that mystify me grub wont boot on it so i had to hack the boot loader.

the question is. i have no security onit apart form tcp wrappers and the firewall on the router.
which is all somewhat iffy.
 whats the best way to get the standard login/mingetty/pam security stuff installed.


ther just doesnt seem  to be much documentation around about this.

ta muchly
neil foster