What is the Active Directory?

What is the Active Directory? : Active Directory (AD) is a database and group of services that links users to the network resources they require to complete their tasks . Important details about your environment are contained in the database (or directory) , including the number of computers and users as well as permissions for each.
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Data are stored as objects in ActiveDirectory. A user, group, application, or thing like a printer are examples of objects. Typically, an object is defined as a resource (such as a computer or printer) or a security principal (such as a user or group).

By name and attributes, Active Directory classifies directory objects. For instance, the name of a user might contain the name string as well as details about the user, like passwords and Secure Shell keys. the features of Active Directory.

Domain Services (AD DS), which manages user communication with the domain and stores directory information, is ActiveDirectory’s primary service. When a user logs into a device or attempts to connect to a server over a network, AD DS verifies access. Group policies and AD DS are used to manage which users have access to each resource. An administrator, for instance, typically has more access to data than an end user.

Other Microsoft and Windows operating system (OS) products, such as Exchange Server and SharePoint Server, rely on AD DS to provide resource access. The server that hosts AD DS is the domain controller.

Table of Contents

Active Directory services

Severaldifferent services comprise Active Directory. The main service is Domain Services, but Active Directory also includes Lightweight Directory Services (AD LDS), Lightweight Directory Access Protocol (LDAP), Certificate Services, or AD CS, Federation Services(AD FS) and Rights Management Services (AD RMS). Each of these other services expands the product’s directory management capabilities.

  • Lightweight DirectoryServices has the same codebase as AD DS, sharing similar functionalities, such as the application program interface. AD LDS, however, can run in multiple instances on one server and holds directory data in a data store using Lightweight Directory Access Protocol.
  • Lightweight Directory Access Protocol is an application protocol used to access and maintain directory services over a network. LDAP stores objects, such as usernames and passwords, in directoryservices, such as Active Directory, and shares that object data across the network.
  • Certificate Services generates, manages and shares certificates. A certificate uses encryption to enable a user to exchange information over the internet securely with a public key.
  • Active Directory Federation Services authenticates user access to multipleapplications — even on different networks — using single sign-on (SSO). As the name indicates, SSO only requires the user to sign on once, rather than use multiple dedicated authentication keys for each service.
  • Rights Management Services control information rights and management. AD RMS encrypts content, such as email or Microsoft Word documents, on a server to limitaccess.

Major features in Active Directory DomainServices

Networked components are synchronized by Active Directory Domain Services using a tier-based layout structure made up of domains, trees, and forests.

Domains are the smallest of the main tiers, while forests are the largest. Different objects, such as users and devices, that share the same database will be on the same domain. A tree is one or more domains grouped together with hierarchical trust relationships. A forest is a group of multiple trees. Forests provide security boundaries,while domains — which share a common database — can be managed for settings such as authentication and encryption.

  • A domain is a group of objects, such as users or devices, that share the same AD database. Domains have a domain name system
  • A tree is one or more domains grouped together. The tree structure uses a contiguous namespace togather the collection of domains in a logical hierarchy. Trees can be viewed as trust relationships where a secure connection, or trust, is shared between two domains. Multiple domains can be trusted where one domain can trust a second, and the second domain can trust a third. Because of the hierarchical nature of this setup, the first domain can implicitly trust the third domain without needing explicit trust.
  • A forest is a group of multiple trees. A forest consists ofshared catalogs, directory schemas, application information and domain configurations. The schema defines an object’s class and attributes in a forest. In addition, global catalog servers provide a listing of all the objects in a forest. According to Microsoft, the forest is Active Directory’s security boundary.
  • Organizational Units (OUs) organize users, groups and devices. Each domaincan contain its own OU. However, OUs cannot have separate namespaces, as each user or object in a domain must be unique. For example, a user account with the same username cannot be created.
  • Containers are similar to OUs, but Group Policy Objects cannot be applied or linked to container objects.
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Trusting terminology

Active Directory relies on trusts to moderate the access rights of resources between domains. There are several different types of trusts:

  • A one-way trust is when a first domain allowsaccess privileges to users on a second domain. However, the second domain does not allow access to users on the first domain.
  • A two-way trust is when there are two domains and each domain enables access to users of the other domain.
  • A trusted domain is a single domain that enables user access to another domain, which is called the trusting domain.
  • Atransitive trust can extend beyond two domains and allow access to other trusted domains within a forest.
  • An intransitive trust is a one-way trust that is limited to two domains.
  • An explicit trust is a one-way, nontransitive trust that is created by a network admin.
  • A cross-link trust is a type ofexplicit trust. Cross-link trusts take place between domains within 1) the same tree, with no child-parent relationship between the two domains, or 2) different trees.
  • A forest trust applies to domains within the entire forest and can be one-way, two-way or transitive.
  • A shortcut joins two domains that belong to separate trees. Shortcuts can be one-way, two-way or transitive.
  • A realm is a trust that is transitive,intransitive, one-way or two-way.
  • An external trust is a trust that links domains across separate forests or domains that are non-AD. External trusts can be nontransitive, one-way or two-way.
  • A private access management (PAM) trust is a one-way trust that is created byMicrosoft Identity Manager between a production forest and a bastion forest.

History and development of Active Directory

With the release of Windows 2000 Server, Microsoft released Active Directory after providing a preview of it in 1999. With each new Windows Server release, Microsoft kept creating new features.

A significant update to Windows Server 2003 added forests and the capacity to edit and move domains within forests. Domains running Windows Server 2000 might not be able to support Server 2003’s more recent AD updates.

AD FS was first made available by Windows Server 2008. Microsoft also changed the name of the domain management directory to AD DS, and AD was used as a catch-all term for all directory-based services that it supported.

Windows Server 2016 updated AD DS to enhance AD security and move AD environments to cloud or hybrid cloud environments. PAM was included in the security updates.

PAM kept track of user actions, the type of access granted, and access to an object. To further secure and secluded the forest environment, PAM added bastion AD forests. Devices running Windows Server 2003 are no longer supported by Windows Server 2016.

In December 2016, Microsoft released Azure AD Connect to join an on-premises Active Directory system with Azure Active Directory (Azure AD) to enable SSO for Microsoft’s cloud services, such as Office 365. Azure AD Connect works with systems running Windows Server 2008, Windows Server 2012,Windows Server 2016 and Windows Server 2019.

Domains vs. workgroups

The workgroup is Microsoft’s term for Windows machines connected over a peer-to-peer network. Workgroups are another unit of organization for Windows computers in networks. Workgroups allow these machines toshare files, internet access, printers and other resources over the network. Peer-to-peer networking removes the need for a server for authentication. There are several differences between domains and workgroups:

  • Domains, unlike workgroups, can host computers from different local networks.
  • Domains can be used to host many more computers than workgroups. Domains can include thousands of computers, unlike workgroups, which typically have an upper limit close to 20.
  • Indomains, at least one server is a computer, which is used to control permissions and security features for every computer within the domain. In workgroups, there is no server and computers are all peers.
  • Domain users typically require security identifiers such as logins and passwords, unlike workgroups.

Main competitors to Active Directory

Red Hat Directory Server, Apache Directory, and OpenLDAP are some of the other directory services available that offer features similar to those of AD.

In Unix environments, Red Hat Directory Server controls user access to numerous systems. Red Hat Directory Server uses user ID and certificate-based authentication, similar to AD, to limit access to directory data.

Any LDAP server, including those running Windows, macOS, and Linux, can use the open source Apache Directory project, which is Java-based. In addition to an LDAP editor and browser, Apache Directory also has a schema browser. Plug-ins for Eclipse are supported by Apache Directory.

OpenLDAP is an open source LDAP directory that runs on Windows. An LDAP server’s objects can be browsed, searched for, and edited by users using OpenLDAP. Among the features of OpenLDAP are the ability to move, copy, and delete directory trees. It also makes it possible to browse schemas, manage passwords, and support LDAP SSL (Secure Sockets Layer).

Read this overview to learn about Active Directory basics.

Find out how replication problems can be fixed and how to troubleshoot common Active Directory problems.

This was last updated in June2021

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What is the Active Directory?

What are the 5 roles of Active Directory? : There are currently five FSMO roles available in Windows: Schema master. Master of domain naming. RID guru. PDC simulator guru of infrastructure.
What are the 3 main components of an Active Directory? : Domains, trees, and forests make up the three main structural elements of Active Directory. A domain is a collection of related objects, such as users or devices, that are connected to the same AD database.
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The fundamental components of Active Directory, known as Active Directory Domain Services (AD DS), manage users and computers while enabling system administrators to arrange the information into logical hierarchies.

Understanding ADDS is a top priority for Incident Response (IR) and cybersecurity practitioners because all cyberattacks will affect AD, and you need to know what to look for and how to respond to attacks when they happen.

Benefits of Active Directory Domain Services

There are several benefits to using AD DS for your basic network user and computer management.

  • You can customize how your data is organized to meet your companies needs
  • You can manage AD DS from any computer on thenetwork, if necessary
  • AD DS provides built in replication and redundancy: if one Domain Controller (DC) fails, another DC picks up the load
  • All access to network resources goes through AD DS, which keeps network access rights management centralized

Active Directory Domain Services Terms toKnow

In order to understand AD DS, there are some key terms to define.

  • Schema: The set of user configured rules that govern objects and attributes in AD DS.
  • Global Catalog: The container of all objects in AD DS. If you need to find the name of a user, that name is stored in the Global Catalog.
  • Query and Index Mechanism: This system allows users to find eachother in AD. A good example would be when you start typing a name in your mail client, and the mail client shows you possible matches.
  • Replication Service: The replication service makes sure that every DC on the network has the same Global Catalog and Schema
  • Sites: Sites are representations of the network topology, so AD DS knows what objects go together to optimize replication and indexing.
  • LightweightDirectory Access Protocol: LDAP is a protocol that allows AD to communicate with other LDAP enabled directory services across platforms.

What Services are Provided in Active Directory Domain Services?

Here are the services that AD DS provides as the core functionalityrequired by a centralized user management system.

  • Domain Services: Stores data and manages communications between the users and the DC. This is the primary functionality of AD DS.
  • Certificate Services: Allows your DC to serve digital certificates, signatures, and public key cryptography.
  • Lightweight Directory Services: Supports LDAP for cross platform domain services, like anyLinux computers in your network.
  • Directory Federation Services: Provides SSO authentication for multiple applications in the same session, so users don’t have to keep providing the same credentials.
  • Rights Management: Controls information rights and data access policies. For example, Rights Management determines if you can access a folder or send an email.

Role of Domain Controllers withActive Directory Domain Services

Domain Controllers (DC) are the servers in your network that host AD DS. DCs respond to authentication requests and store AD DS data. DCs host other services that are complementary to AD DS as well. Those are:

  • Kerberos Key Distribution Center (KDC): The kdc verifies and encryptskerberos tickets that AD DS uses for authentication
  • NetLogon: Netlogon is the authentication communication service.
  • Windows Time (W32time): Kerberos requires all computer times to be in sync.
  • Intersite Messaging (IsmServ): Intersite messaging allows DCs to communicate with eachother for replication and site-routing.

One domain controller is a minimum requirement for AD. The domains are kept in containers called DCs. Every domain is a part of the AD Forest, which may contain one or more domains that are divided into organizational units. Because AD DS manages trusts between different domains, you can grant other users in your forest access rights for users in one domain.

The most crucial idea to grasp is that the computer users use to access AD is the DC, and that AD DS is a framework for domain management.

A thorough understanding of Active Directory is essential for modern cybersecurity. Attackers’ ability to infiltrate networks, move laterally, and exfiltrate data all depend on Active Directory. Attackers leave breadcrumbs in AD logs as they move through your network, regardless of how cunning or stealthy they are.

Varonis keeps an eye on AD for these breadcrumbs as well as file activity, DNS calls, VPN activity, and other things. Varonis combines this information into a comprehensive picture for each user and computer in AD, compares the activity to a normalized baseline and a collection of threat models for data security, and proactively spots potential threats to your data.

Check out our on-demand webinar, “4 Tips to Secure Active Directory,” for more information on AD security.

Jeff Petters

Since his father brought home an IBM PC 8086 with dual disk drives, Jeff has been working on computers. His ideal job would be to conduct research and write about data security.

[/lightweight-accordion]What is example of Active Directory? : The domain name ad-internal is a good illustration of an Active Directory name. company. com, where ad-internal denotes the name of your company’s internal AD domain. Your external resources go by the name of com.
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Conrad Agramont, CEO of Agile IT, talks about the seven types of Active Directory in this Tech Talk, what each one is used for, and how they can work together to deliver solutions. See the following tech talks and articles on Active Directory from our archives:

The Shared Responsibility Model


Applications Customer Customer Customer Provider
Data Customer Customer Customer Provider
Runtime Customer Customer Provider Provider
Middleware Customer Customer Provider Provider
O/S Customer Customer Provider Provider
Virtualization Customer Provider Provider Provider
Servers Customer Provider Provider Provider
Storage Customer Provider Provider Provider
Networking Customer Provider Provider Provider

What is Active Directory?

Active Directory (AD), introduced in 1999 as part of Windows Server 2000, is a directory service based on Lightweight Directory Access Protocol (LDAP). AD is responsible for authenticating and authorizing all users and computers in a windows domain network.

  • People
    • Names
    • Numbers
    • Address
  • Services
    • Category
    • Names
    • Numbers
    • Address
    • Advertisement
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The Types of Active Directories

There are technically 7 different types of Active Directory. Each of them are deployed in different way, places and for different purposes.

Active Directory TypeDeploymentModern?Purpose

Local AD (AD) Server No Local Identity
Active Directory Federation Services (ADFS) Server No Single Sign On (SSO) For Ad
Azure Active Directory Cloud Yes Cloud Identity
Azure Active Directory Domain Services Cloud Yes Cloud Hybrid Servers
Azure Active Directory Connect Server Sync AD and AAD
Azure Active Directory Connect Cloud Provisioning Server Yes Sync AD and AAD (Limited)
Azure Active Directory Application Proxy Cloud Yes Azure AD enable legacy apps

Identity is Your Control Plane

What is Local Active Directory (AD)


  • Centralized administration for servers, workstations, users, and applications
  • Services(e.g. Exchange) can leverage for email services configuration


  • Windows Server OS
  • Active Directory Domain Controllers


  • Requires direct network connection
  • Reliance on customer managed networking: DNS, VPN, and Servers (Physical and Virtual)

What is Azure Active Directory (AAD)


  • Centralized administration for cloud services
  • Services (e.g. Exchange) can leverage foremail services configuration
  • Hybrid scenarios supported via Azure AD Connect connecting to local Active Directory
    • Use your corporate credentials/passwords


  • Cloud Service


  • Lack of IT protection without AAD P1 and P2 licensing
  • Device bases security requires EM+S licensing for Intune

What is Azure AD Connect Cloud Provisioning?

Enterprise and standard versions are $60 and $300, respectively; the difference is the number of objects.

(Make table from slide)

What is Azure Active Directory Domain Services (AADDS)


  • Local Active Directory (Fully compatible with Windows Server Active Directory)
  • Lift and Shift scenarios for Windows servers
    • Use your corporate credentials/passwords
    • NTLM and Kerberos authentication
  • Co-mingle local Active Directory users and Azure Active Directory users


  • Cloud Service (Two domain controllers are available by IP only)
  • Highly available domain
  • Auto-remediation
  • Automatic backups


  • Organizational Units are flat and not brought over from local AD/AAD
  • Not recommended for workstations
  • Administrators are NOT Domain Admins (it’s also a good thing)

Synced Tenants

What is Azure AD Application Proxy


  • Publish on-premises web apps externally in a simplified way without a DMZ
  • Support single sign-on (SSO) across devices, resources, and apps in the cloud and on-premises
  • Support multi-factor authentication for apps in the cloudand on-premises


  • Requires Azure AD basic or premium (P1 or P2) subscription
  • Support Authentication: Integrated Windows Authentication (IWA), Header-based, forms, password-based SAML


  • Connector must be installed on Windows Server 2102 R2 or higher, Windows 8.1 or higher
  • The on-premises firewall must be enabled for outbound traffic from the connector

Up Next? Getting Rid of Your Local ActiveDirectory

Local Active Directories are becoming redundant and occasionally difficult pieces of infrastructure as more businesses move more of their operations to the cloud. Agile IT made the bold move to remove our own Local Active Directory last year, and since then, we’ve assisted dozens of businesses in doing the same. In an upcoming Tech Talk, Conrad will talk about the risks, difficulties, and advantages of deleting your own local active directory.


Additional Question — What is the Active Directory?

What is the main purpose of Active Directory?

Microsoft’s exclusive directory service is called Active Directory (AD). Administrators can control who has access to network resources thanks to its Windows Server-based operation. Data are stored as objects in Active Directory. A user, group, application, or thing like a printer are all examples of objects.

How many types of Active Directory are there?

Active Directory comes in 7 different varieties in theory. They are all used in various capacities, settings, and for various objectives.

What are the 4 most important benefits of Active Directory?

Centralized resource management and security administration are advantages and benefits of Active Directory. Access to all resources requires only one logon. simplified location of the resource.

What is a domain in Active Directory?

An Active Directory domain is a collection of objects within a Microsoft Active Directory network. An object can be a single user or a group or it can be a hardware component, such as a computer or printer. Each domain holds a database containing object identity information.

What is Active Directory and LDAP?

Microsoft’s AD is a directory service that restricts access to critical personal data about people inside of a specific organization. Meanwhile, users can query an AD and authenticate access to it using the non-Microsoft LDAP protocol.

What is Active Directory and its uses and benefits?

Domains built on Active Directory allow for centralized management. One environment can be used to manage data pertaining to accounts, groups, and network resources. Active Directory enables users to log in once to access all network resources if a business only needs one location.

What are the features of Active Directory?

Basic Directory FeaturesFeatureDescriptionObject dataAble to store user, group, organization, and service data in a hierarchical treeRich queryAble to locate an object by querying for object properties1 more row. Location transparencyAble to find user, group, networked service, or resource, data without the object address.

What is the disadvantage of Active Directory?

Windows-Only Solution: Active Directory is only compatible with Windows. LDAP (Lightweight Directory Access Protocol) clients, as opposed to an Active directory, are needed to manage Linux or Mac computers.

What is AD and how IT works?

Running on Microsoft Windows Server is the directory service known as Active Directory (AD). Active Directory’s primary purpose is to give administrators the ability to manage permissions and restrict access to network resources.

What are the benefits of Active Directory?

Benefits of Active Directory Domain ServicesYou can tailor the organization of your data to suit the requirements of your business. You can manage AD DS from any computer on the network, if necessary If one Domain Controller (DC) fails, another DC takes over the workload thanks to AD DS’s built-in replication and redundancy.

Is Active Directory an LDAP?

Active Directory is a directory server that uses the LDAP protocol.

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