network resources must be availabe only for users who logged into domain

I have a win 2003 DC.
I want to restrict the network resources only for those who are logged into domain.(B’coz now they just log-in as local users and access resources by entering domain username/pswd after that. Can we define a group policy for this?Or we need to do this by global security group permissions?if so how?

Plz help me .
thanks in advance