Attacking a machine on network.

Dear list,

Is it possible at all that there are avenue of possible attack if not
even one port is listed as listening on a network ?

If someone doesn't run a service, this obviously leads me to the
assumption that that particular machine could never be cracked ? Is this
a right assumption ?

Also, most of the attack on server seems to be some kind of buffer
overflow attack, crafted packets, and DOS. Also such that these are
especially true for those machines which *listen* on a network
interface. How do attackers then basically able to mount an attack on a
machine which doesn't listen to any network interface ?

Are there any papers/text books I can refer to further ?

Thanks for your time.