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Security Fundamentals & Crypto · Foundational

Active Directory (AD)

Microsoft's on-premises directory service for Windows domains, using LDAP, Kerberos, and DNS.

Definition

Active Directory Domain Services stores users, computers, and groups in a hierarchy of forests, domains, and organizational units. Domain controllers provide authentication via Kerberos and NTLM and apply Group Policy. AD is a prime attack target, so tiered administration and hardening are critical.

Example

An administrator links a GPO to the Workstations OU to enforce screen lock and BitLocker.

Exam tip

AD is on-premises; Microsoft Entra ID is the cloud identity service. They are not the same product.

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