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# 6.1.1 Introduction to Active Directory (AD)
## **Active Directory Overview**
### What is Active Directory (AD)?
[**Active Directory**](https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/get-started/virtual-dc/active-directory-domain-services-overview) **(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.
***
## **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.
***
## **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.
***
## **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).
***
## **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.
