In a modern Microsoft environment, the Active Directory database is arguably one of the essential assets of the network. Thus protecting AD is an important part of maintaining a productive environment. In previous tips I've discussed how to lock down domain controllers and manage access to AD. Now, I want to talk about increasing security by locking down the desktop systems that administrators use to interact with AD.
One of the most secure configurations of administrator user accounts is to limit them so they can log on only to a single specific workstation. When configured thus, the administrator account is useless to anyone attempting to log on to the network from any other system other than the one assigned to the account. This configuration can be accomplished through the following procedures:
- Move the administrator's workstation into a sub-OU specifically created to host administrator workstations.
- Modify the domain level GPO to set the Deny log on locally user rights assignment control for all of the following admin groups: Schema Admins, Enterprise Admins, Domain Admins, Server Operators, Backup Operators, and Account Operators.
- Create a GPO on the sub-OU. Define the Deny log on locally user rights assignment control, but leave it blank.
- Next, set the Log On To controls on each administrator account to the specific workstation assigned to that operator.
In this way, the sub-OU's GPO will over-ride the domain level GPO for that control, thus allowing admins to log on to the workstations in the sub-OU but not to any other system in the domain.
This configuration will not prevent the local administrator account on each system from being able to log on to its local system, but it does a great job of locking down domain administrators.
Obviously, this configuration will require that these administrative groups have the right logon across the network for the server's they have to manage. And you may need to create special sub-OUs to host member servers and domain controllers in the same fashion.
BTW: using the Log On To control through a user account's properties is the only means to effectively enforce or restrict the ability of a single user account to log in only once to a domain. By assigning a single workstation, the account is effectively limited to a single logon. If a user account has more than one workstation assigned or is not restricted to a set of workstations, that one user account can be logged on to multiple systems simultaneously.
James Michael Stewart is a partner and researcher for ITinfopros, a technology-focused writing and training organization.