Active Directory(AD) is a directory service used by Windows to facilitate many services required to manage an organization’s network of users and resources.

Now let us dive deep into Active Directory and get a more clearer picture of what actually it is.

Directory service:

A directory service is a service that stores objects as a collection of bindings between names and attributes from which we can lookup entries, from a hierarchical structure, that match a specific attribute. These objects can be users or any other electronic equipment. They are sometimes referred to as attribute-based name services or more colloquially “yellow/white page services”. Some popular examples are Microsoft’s Active Directory, X.500, LDAP etc…

Directory service is much like a phone book which stores information as objects (computers, printers etc…). It provides hierarchical structure to store objects for quick and easy access. It is the means by which users and administrators can locate resources regardless of where those resources are located. It stores and returns a set of attributes related to objects. Here, consider objects to be as the same object representation in object-oriented languages (just for better understanding). For example, the request ‘EmpId=123’ would return {EmpId=123, Name=”Sam”, Email=”sam@gmail.com”}.

Active Directory (AD):

AD is a directory service used by windows. Active directory stores directory objects by a set of name and attributes. For example, the name of a user as a string, along with other information associated with the user, such as passwords. It also makes user management easier as it acts as a single repository for storing all user and computer related information. It controls which users have access to each resource with its group policies.

Active Directory take care of authentication by using Kerberos authentication and Single Sign-On (SSO). SSO means ability of Kerberos to provide a user with one set of credentials and grant them access across a range of resources and services with that same set of credentials. AD authenticates using Kerberos tickets. Non windows devices use RADIUS or LDAP to authenticate to AD. Kerberos authenticates the credentials and issues the user a ticket with which the user gains access to the resources and services.

Physical components of AD:

1. Domain Controllers:

It is the head honcho of all servers. It hosts AD Domain Services (AD DS) directory store. This is main component which has admin privileges. It stores information of all other devices and manages user accounts. It responds to authentication requests, assigns and enforces security policies. We can make it to periodically replicate updates to other domain controllers.

2. AD data stores:

These data stores contain “ntds.dit” file which is a very important file. It contains objects, groups and password hashes. It is stored in “%SystemRoot%\NTDS” folder in domain controller. These data stores are only accessible through domain controller processes.

Logical Components of AD:

1. Schema:

A schema contains definitions of every object that is in the directory. It also enforces rules regarding object creation and configuration.

2. Domains:

Domains are the administrative boundaries of the organization by which policies can be applied and the scope of access to the resources can be limited. It is a partition in the AD forest. Objects made in AD are grouped into domains.

3. Trees:

Trees are a hierarchical collection of domains in a DS. They share a common namespace with the parent domain.

4. Forest:

Forest is a collection of one or more domain trees that share a common global catalog (to enable searching), directory schema, logical structure and directory configuration.

5. Organizational Units (OU):

OUs are directory containers that contain users and groups, maybe other OUs. They are used to apply policies and permissions.

6. Trusts:

A trust is a mechanism to gain access to resources in a domain. There are two types of trusts: Directional Trust and Transitive Trust. All domains in a forest trust all other domains in the same forest. Trust can be made to extend outside the forest too.

7. Objects:

Objects are the individual components in an organization. They fall into two categories: Resources and Security policies.

That’s all you need to know to get started in Active Directories. Go ahead, put on your thinking caps and research more on the topic !

For any queries, explanations or blog suggests, feel free to contact me on Twitter @monishpalani

Cybersecurity enthusiast. Full stack developer