Access granted even on root password change

[Vinicius Pavanelli Vianna]

Hi,

How could I afford that i can get always access to my remote server even
in the case of a breakin by some script kiddie/hack? I thought about
setting a key in ssh so i can log using it even the root password is
changed, but this is simple to stop and it's not good to assume lack of
knowledge of others ;)
Anyone knows a good backup access system, like a rootkit for FreeBSD?

TIA,
Vinicius