6.1.1 Introduction to Active Directory (AD)

Active Directory Overview

What is Active Directory (AD)?

Active Directory (AD) is directory service developed by Microsoft to manage Windows domain networks and it is the most commonly used indentity management service in the world (95% of companies use it),

Active Directory is like a phone book that stores all kinds of informations related to different kind of objects, such as: computers, users, printers, etc. In this case, we can store info regarding:

• Windows User: Account Info, Privileges, Profiles, Policy;

• Windows Servers: Managament Profile, Network Information, Printers, File Shares, Policy;

• Windows Clients: Managament Profile, Network Information, Policy;

• Network Devices: Configuration, Quality of Service Policy, Security Policy;

• Firewall Services: Configuration, VPN Policy, Security Policy;

• Applications: Server Configuration, Single Sign-on, Application Specific Directory Information;

• E-Mail Servers: Mailbox Info, Address Book;

• Other NDS: User Registry, Security Policy.

All these info can be allocated throughout multiple location and AD permits centralization with: Manageability, Security and Interoperability.

It permits the authentication of computers in the network using relative credentials via Kerberos tickets methodology.

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Active Directory Components

1. Domains:

   • Logical grouping of network objects (e.g., users, computers) managed as a single unit. Domains share security policies and directory databases.

2. Domain Controllers (DCs):

   • Servers responsible for authenticating logins and enforcing security policies.

   • Hold a copy of the AD database for redundancy and synchronization.

3. Forests and Trees:

   • A forest is the top-level container housing multiple domains that share a schema and configuration.

   • Domains within a forest are structured as trees, connected hierarchically for trust and resource access.

4. Organizational Units (OUs):

   • Logical containers within a domain for organizing objects like users, groups, and computers.

   • Facilitate delegation of administrative responsibilities and targeted GPO applications.

5. Global Catalog (GC):

   • A partial, read-only copy of the entire forest's objects.

   • Speeds up cross-domain queries.

6. Trust Relationships:

   • Define how domains within a forest or between forests share authentication and authorization information.

   • Types: One-way, two-way, transitive, or non-transitive.

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Managing Networks with AD

Small Networks:

In networks with fewer than 10 devices:

• Administration is manual and direct.

• Each system requires individual configuration and troubleshooting.

Enterprise Networks:

In larger organizations like "Foo Bank Inc." with 100+ devices:

• Manual management is infeasible.

• AD centralizes all tasks, from user account management to software updates, ensuring scalability and efficiency.

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Authentication in AD

1. Kerberos Protocol:

   • The default and secure method of authentication.

   • Employs ticket-based mechanisms:

     • Ticket Granting Ticket (TGT): Central to Single Sign-On (SSO).

     • Features: Mutual authentication, reduced credential exposure.

2. NTLM Protocol:

   • Legacy protocol for older systems.

   • Simpler but prone to vulnerabilities like Pass-the-Hash (PtH).

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Users, Groups, and Computers in AD

1. Domain Users:

   • Represent individuals with unique credentials for accessing resources.

   • Attributes like job title and department can be tied to accounts.

2. Groups:

   • Security Groups: Assign permissions for resource access.

   • Distribution Groups: Facilitate email distribution without security functions.

3. Computers:

   • Represent devices joined to the domain.

   • Have unique computer accounts for resource authentication.