# What is Active Directory (AD)?

> Active Directory (AD) usually refers to Microsoft Active Directory Domain Services (AD DS), a distributed directory and identity service for Windows domain environments.

- Canonical URL: https://yellowcube.eu/glossary/active-directory/
- Publisher: Yellow Cube
- Language: en
- Contact: hello@yellowcube.eu

## Content

It stores objects such as users, groups, computers, services, and policies, and lets domain controllers provide authentication, directory queries, replication, and authorization data to joined systems and applications.

AD DS organizes objects into domains and organizational units, with one or more domains forming a forest. It relies heavily on the Domain Name System (DNS), uses protocols including Kerberos and the Lightweight Directory Access Protocol (LDAP), and supports policy administration through Group Policy. Because applications and administrators often depend on it, AD DS is part of the organization’s identity control plane.

### Key points

- **Directory structure:** The schema defines object types and attributes; domains partition directory data, and domain controllers replicate it.
- **Trust and delegation:** Forest and domain trusts can extend authentication paths, while groups, access-control lists, and delegated administration influence effective authority.
- **Operational priorities:** Protect domain controllers and privileged administration, secure backups and recovery, monitor sensitive changes, and retire weak protocols and obsolete dependencies where feasible.
- **Important limitation:** Centralization does not make access correct or secure by itself. A compromised domain controller, privileged identity, trust, or replication path can create broad impact, while legacy applications may preserve weaker authentication and excessive privilege.

### Related terms

[Kerberos authentication](<https://yellowcube.eu/glossary/kerberos-authentication/>) · [Lightweight Directory Access Protocol (LDAP)](<https://yellowcube.eu/glossary/lightweight-directory-access-protocol/>) · [Service account](<https://yellowcube.eu/glossary/service-account/>) · [Privileged access management (PAM)](<https://yellowcube.eu/glossary/privileged-access-management/>) · [Domain Name System (DNS) security](<https://yellowcube.eu/glossary/domain-name-system-security/>)

### Sources

[Microsoft: Active Directory Domain Services overview](https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/get-started/virtual-dc/active-directory-domain-services-overview) · [Microsoft: Active Directory logical model](https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/plan/understanding-the-active-directory-logical-model) · [Microsoft: Compare directory-based identity services](https://learn.microsoft.com/en-us/entra/identity/domain-services/compare-identity-solutions)

## Attribution and scope

This Markdown representation is generated from the same approved content records as the canonical HTML page. Cite the canonical URL above when referencing this material. Product and service descriptions are informational; confirm project-specific requirements with Yellow Cube.