Knowledge is Power

Active Directory Domain Services (AD DS) improve the ability for organizations to secure Active Directory environments and help them migrate to cloud-only deployments and hybrid deployments, where some applications and services are hosted in the cloud and others are hosted on premises

Privileged access management

Privileged access management (PAM) helps mitigate security concerns for Active Directory environments that are caused by credential theft techniques such pass-the-hash, spear phishing, and similar types of attacks. It provides a new administrative access solution that is configured by using Microsoft Identity Manager (MIM). PAM introduces:
A new bastion Active Directory forest, which is provisioned by MIM. The bastion forest has a special PAM trust with an existing forest. It provides a new Active Directory environment that is known to be free of any malicious activity, and isolation from an existing forest for the use of privileged accounts. New processes in MIM to request administrative privileges, along with new workflows based on the approval of requests.
New shadow security principals (groups) that are provisioned in the bastion forest by MIM in response to administrative privilege requests. The shadow security principals have an attribute that references the SID of an administrative group in an existing forest. This allows the shadow group to access resources in an existing forest without changing any access control lists (ACLs).
An expiring links feature, which enables time-bound membership in a shadow group. A user can be added to the group for just enough time required to perform an administrative task. The time-bound membership is expressed by a time-to-live (TTL) value that is propagated to a Kerberos ticket lifetime.
KDC enhancements are built in to Active Directory domain controllers to restrict Kerberos ticket lifetime to the lowest possible time-to-live (TTL) value in cases where a user has multiple time-bound memberships in administrative groups. For example, if you are added to a time-bound group A, then when you log on, the Kerberos ticket-granting ticket (TGT) lifetime is equal to the time you have remaining in group A. If you are also a member of another time-bound group B, which has a lower TTL than group A, then the TGT lifetime is equal to the time you have remaining in group B.
New monitoring capabilities to help you easily identify who requested access, what access was granted, and what activities were performed.

Deprecation of File Replication Service (FRS) and Windows Server 2003 functional levels

Although File Replication Service (FRS) and the Windows Server 2003 functional levels were deprecated in previous versions of Windows Server, it bears repeating that the Windows Server 2003 operating system is no longer supported. As a result, any domain controller that runs Windows Server 2003 should be removed from the domain. The domain and forest functional level should be raised to at least Windows Server 2008 to prevent a domain controller that runs an earlier version of Windows Server from being added to the environment.
At the Windows Server 2008 and higher domain functional levels, Distributed File Service (DFS) Replication is used to replicate SYSVOL folder contents between domain controllers. If you create a new domain at the Windows Server 2008 domain functional level or higher, DFS Replication is automatically used to replicate SYSVOL. If you created the domain at a lower functional level, you will need to migrate from using FRS to DFS replication for SYSVOL. For migration steps, you can either follow the procedures on TechNet or you can refer to the streamlined set of steps on the Storage Team File Cabinet blog.
The Windows Server 2003 domain and forest functional levels continue to be supported, but organizations should raise the functional level to Windows Server 2008 (or higher if possible) to ensure SYSVOL replication compatibility and support in the future. In addition, there are many other benefits and features available at the higher functional levels higher.