What is Active Directory ?

Active Directory (AD) is a directory service developed by Microsoft that provides a centralized location for managing and organizing resources in a networked environment. It serves as a repository for storing information about user accounts, computers, groups, and other network resources.

Active Directory is designed to simplify network administration by providing a hierarchical structure and a set of services that enable administrators to manage user authentication, authorization, and access to resources efficiently.

How does Active Directory work?

Active Directory works by organizing objects into a hierarchical structure called a domain. Domains can be grouped together to form trees, and multiple trees can be connected to create a forest. The domain controller acts as the central server that authenticates and authorizes users, maintains the directory database, and replicates data to other domain controllers within the same domain or across domains. Clients interact with the domain controller to request authentication and access to network resources.

Active Directory operates as the authentication infrastructure in practically almost every organizational network today. In the pre-cloud era, all the organizational resources resided exclusively on-premise, making AD effectively the sole identity provider. 

However, even at a time when organizations seek to transit workloads and applications to the cloud, AD is still present in more than 95% of organizational networks. This is mainly due to core resources being hard or impossible to migrate to the cloud.

What are the 3 main functions of Active Directory?

  1. Authentication: Active Directory is used to authenticate users, computers, and other resources on a network. This means that AD verifies the identity of a user or device before allowing access to network resources.
  2. Authorization: Once a user or device has been authenticated, AD is used to authorize access to specific resources on the network. This is done by assigning permissions and rights to users and groups, which determine what they are allowed to do on the network.
  3. Directory Services: Active Directory is also a directory service, which means that it stores and organizes information about network resources, such as users, computers, and applications. This information can be used to manage and locate resources on the network.

Relationship to Azure Active Directory

Azure Active Directory (Azure AD) is Microsoft’s cloud-based identity and access management service. While Active Directory is primarily used for on-premises network environments, Azure AD extends its capabilities to the cloud. Azure AD provides features such as single sign-on (SSO), multi-factor authentication (MFA), and user provisioning for cloud applications and services. It can also synchronize user accounts and passwords from an on-premises Active Directory to Azure AD, allowing organizations to manage user identities consistently across on-premises and cloud environments.

Benefits of Active Directory

Active Directory offers several benefits for organizations:

  • Centralized User Management: Active Directory provides a centralized location to manage user accounts, groups, and access to resources. This simplifies the administration of user identities and enhances security by enabling consistent access control policies.
  • Single Sign-On (SSO): Active Directory supports SSO, allowing users to authenticate once and access multiple resources without needing to re-enter credentials. This improves user experience and reduces the need for remembering multiple passwords.
  • Resource Management: Active Directory facilitates efficient management of network resources such as computers, printers, and file shares. It enables administrators to organize and secure resources based on user or group permissions, ensuring proper access control.
  • Group Policy Management: Active Directory allows administrators to define and enforce security policies, configurations, and restrictions across the network using Group Policy Objects (GPOs). GPOs enable consistent application of security settings and help maintain compliance with organizational standards.

Vulnerabilities in Active Directory

While Active Directory provides robust security features, it is not immune to vulnerabilities. Some common vulnerabilities include:

  • Credential Attacks: Attackers may attempt to compromise user credentials through techniques like password cracking, phishing, or credential theft. Weak or easily guessable passwords can be exploited to gain unauthorized access to the Active Directory.
  • Privilege Escalation: If an attacker gains access to a low-privileged account, they may try to escalate privileges within the Active Directory environment. This can lead to unauthorized access to sensitive resources or administrative privileges.
  • Lateral Movement: Once inside the Active Directory, attackers may exploit weak access control or misconfigurations to move laterally within the network, escalating their access and potentially compromising additional resources.
  • Active Directory Replication Vulnerabilities: The replication process in Active Directory may have vulnerabilities that attackers can exploit to manipulate or inject malicious data into the directory database, leading to unauthorized access or disruptions in the replication process.
  • Active Directory cannot detect or prevent Identity Threats: AD cannot provide protection against these attacks since its protection capabilities are limited to checking the match between username and credentials. Since identity threats, by definition, are founded on compromising valid usernames and credentials they can easily bypass AD and impersonate their malicious authentication as a legitimate one. This creates a severe blind spot in organizations’ security architecture that gives rise to numerous variations of lateral movement attacks.

It is crucial for organizations to implement strong security measures, such as regular patching, robust password policies, multi-factor authentication, and monitoring, to mitigate these vulnerabilities and protect the integrity and security of their Active Directory environment.

Active Directory Structure

Components of Active Directory

Active Directory is structured using three main components: domains, trees, and forests. A domain is a logical grouping of objects, such as user accounts, computers, and resources, within a network. Domains can be combined to form a tree, which represents a hierarchical structure where child domains are connected to a parent domain. Multiple trees can be linked together to create a forest, which is the highest level of organization in Active Directory. Forests enable the sharing of resources and trust relationships between domains within the same organization or across different organizations.

Hierarchical structure of Active Directory

Domains in Active Directory follow a hierarchical structure, with each domain having its own unique domain name. Domains can be further divided into organizational units (OUs), which are containers used for organizing and managing objects within a domain. OUs provide a way to delegate administrative tasks, apply group policies, and define access permissions at a more granular level. OUs can be nested within each other to create a hierarchy that aligns with the organization’s structure, making it easier to manage and control access to resources.

Trust  and how it enables secure communication between domains

Trust relationships in Active Directory establish secure communication and resource sharing between different domains. A trust is a relationship established between two domains that enables users in one domain to access resources in the other domain. Trusts can be transitive or non-transitive. Transitive trusts allow trust relationships to flow through multiple domains within a forest, while non-transitive trusts are limited to a direct relationship between two specific domains. Trusts enable users to authenticate and access resources across trusted domains, providing a cohesive and secure environment for collaboration and resource sharing within and between organizations.

Active Directory Architecture and Components

Domain Controllers

Domain controllers are key components of Active Directory architecture. They serve as the central servers responsible for authenticating and authorizing user access, maintaining the directory database, and handling directory-related operations within a domain. In a domain, there is typically one primary domain controller (PDC) that holds the read-write copy of the directory database, while additional backup domain controllers (BDCs) maintain read-only copies. Domain controllers replicate and synchronize data using a process called replication, ensuring that changes made in one domain controller are propagated to others, thus maintaining a consistent directory database across the domain.

Global Catalog Servers

Global catalog servers play a vital role in Active Directory by providing a distributed and searchable catalog of objects across multiple domains within a forest. Unlike domain controllers that store information specific to their domain, global catalog servers store a partial replica of all domain objects in the forest. This enables faster searching and access to information without the need for referrals to other domains. Global catalog servers are beneficial in scenarios where users need to search for objects across domains, such as finding email addresses or accessing resources in a multi-domain environment.

Active Directory Sites and Replication

Active Directory sites are logical groupings of network locations that represent physical locations within an organization, such as different offices or data centers. Sites help manage network traffic and optimize authentication and data replication within the Active Directory environment. Site links define the network connections between sites and are used to control the replication traffic flow. Site link bridges provide a way to connect multiple site links, allowing efficient replication between non-adjacent sites. The replication process ensures data consistency by replicating changes made in one domain controller to other domain controllers within the same site or across different sites. This process helps maintain a synchronized and up-to-date directory database across the network, ensuring that changes are propagated reliably throughout the Active Directory infrastructure.

Active Directory Services

Active Directory Domain Services (AD DS)

AD DS is the primary service within Active Directory that handles authentication and authorization. It verifies the identity of users and grants them access to network resources based on their permissions. AD DS authenticates users by validating their credentials, such as usernames and passwords, against the directory database. Authorization determines the level of access users have to resources based on their group memberships and security principles.

User accounts, groups, and security principles in AD DS

User accounts, groups, and security principles are fundamental components of AD DS.

User accounts represent individual users and contain information such as usernames, passwords, and attributes like email addresses and phone numbers.

Groups are collections of user accounts that share similar permissions and access rights. They simplify access management by allowing administrators to assign permissions to groups rather than individual users.

Security principles, such as security identifiers (SIDs), uniquely identify and secure objects within AD DS, providing a foundation for access control and security.

Domain controllers and their roles in AD DS

Domain controllers are servers that host AD DS and play a vital role in its functioning. They store and replicate the directory database, handle authentication requests, and enforce security policies within their domain. Domain controllers maintain a synchronized copy of the directory database, ensuring consistency across multiple domain controllers. They also facilitate the replication of changes made in one domain controller to others within the same domain or across domains, supporting fault tolerance and redundancy within the AD DS environment.

Active Directory Federation Services (AD FS)

AD FS enables Single Sign-On (SSO) across different organizations and applications. It acts as a trusted intermediary, allowing users to authenticate once and access multiple resources without the need for separate logins. AD FS provides a secure and seamless authentication experience by leveraging standard protocols such as Security Assertion Markup Language (SAML) and OAuth. It eliminates the need for users to remember multiple credentials and simplifies the management of user access across organizational boundaries.

How AD FS establishes trust relationships between organizations

AD FS establishes trust relationships between organizations to enable secure communication and authentication. Trust is established through the exchange of digital certificates between the identity provider (IdP) and the relying party (RP). The IdP, typically the organization providing identity information, issues and verifies security tokens containing user claims. The RP, the resource or service provider, trusts the IdP and accepts the security tokens as proof of user authentication. This trust relationship allows users from one organization to access resources in another organization, enabling collaboration and seamless access to shared services.

Active Directory Lightweight Directory Services (AD LDS)

AD LDS is a lightweight directory service provided by Active Directory. It serves as a directory solution for lightweight applications that require directory functionalities without the need for a full AD DS infrastructure. AD LDS offers a smaller footprint, simplified management, and a more flexible schema than AD DS. It is commonly used in scenarios such as web applications, extranets, and line-of-business applications that require directory services but do not necessitate the complexity of a complete Active Directory deployment.

Key features of Active Directory Lightweight Directory Services

Key features of AD LDS include the ability to create multiple instances on a single server, which allows different applications or services to have their own isolated directory. AD LDS provides a flexible and extensible schema that can be customized to suit specific application requirements. It supports lightweight replication to synchronize directory data across instances, enabling distributed and redundant directory services. Use cases for AD LDS include storing user profiles for web applications, providing directory services for cloud-based applications, and supporting identity management for line-of-business applications that require a separate directory store.

Active Directory Certificate Services (AD CS)

Active Directory Certificate Services (AD CS) is a service within Active Directory that plays a crucial role in issuing and managing digital certificates. AD CS enables organizations to establish secure communications, verify the identity of users or devices, and establish trust within their network environment. It provides a centralized platform for issuing and managing digital certificates, which are used to encrypt data, authenticate users, and ensure the integrity of transmitted information.

By leveraging AD CS, organizations can enhance the security of their communications, protect sensitive data, and establish trust relationships with internal and external entities. The benefits of AD CS include improved data confidentiality, secure access to resources, enhanced authentication mechanisms, and compliance with industry regulations. AD CS empowers organizations to build a robust security infrastructure and establish a foundation of trust in their network environment.

Active Directory Security

Authentication and Authorization

Authentication is a crucial step in Active Directory’s security framework. When a user attempts to access network resources, Active Directory verifies their identity by checking the provided credentials against stored user account information. This process involves validating the username and password combination or employing other authentication protocols like Kerberos or NTLM.

Active Directory supports these protocols to ensure secure and reliable authentication. Once the user is authenticated, Active Directory performs authorization, determining the level of access they have based on their assigned permissions and group memberships. Effective authorization controls ensure that only authorized individuals can access specific resources, thereby minimizing the risk of unauthorized access and potential security breaches.

Group Policy Objects (GPOs)

Group Policy Objects (GPOs) are a powerful tool within Active Directory for enforcing security policies and configuration settings across the network. GPOs define rules and settings that apply to users and computers within specific organizational units (OUs). They allow administrators to implement security measures consistently and efficiently. For example, GPOs can enforce password complexity requirements, define account lockout policies, and restrict the execution of unauthorized software.

By utilizing GPOs effectively, organizations can establish a standardized security baseline, reducing the risk of misconfigurations and enhancing the overall security posture of the network.

Active Directory Security Best Practices

As the reliance on AD grows, it becomes crucial to implement robust security practices to protect against potential threats. In this article, we will explore key security considerations and best practices for securing Active Directory, focusing on the importance of strong passwords and password policies, implementing multi-factor authentication (MFA), and the role of auditing in maintaining a secure environment.

Key Security Considerations for Securing Active Directory:

Securing Active Directory requires a comprehensive approach that addresses various aspects of its infrastructure. Some essential security considerations include:

  • Regular Patching: Keeping Active Directory servers up to date with the latest security patches is vital to mitigate vulnerabilities. Regularly applying patches and updates helps protect against known exploits and reduces the risk of unauthorized access.
  • Least Privilege Principle: Implementing the principle of least privilege ensures that users have only the necessary permissions to perform their tasks. By granting minimal privileges, organizations can limit potential damage in the event of compromised accounts or insider threats.
  • Secure Network Infrastructure: Maintaining a secure network infrastructure is essential for protecting Active Directory. Implementing firewalls, intrusion detection and prevention systems, and robust network segmentation enhances the overall security posture of the network and mitigates the risk of unauthorized access.

Importance of Strong Passwords and Password Policies:

Strong passwords play a critical role in preventing unauthorized access to Active Directory resources. Implementing strong password policies ensures that users create and maintain secure passwords. Password policies should enforce complexity requirements, such as minimum length, a mix of uppercase and lowercase characters, numbers, and special symbols. Regular password expiration and the prevention of password reuse are also crucial to maintain strong authentication practices. Educating users about the importance of creating unique and robust passwords can further enhance password security.

Can Active Directory be synced with an IAM that manages access to SaaS apps?

Yes, it is possible to sync or federate Active Directory (AD) with another Identity and Access Management (IAM) solution that manages access and Single Sign-On (SSO) for SaaS applications. This integration allows organizations to leverage the existing user accounts and groups in AD while extending their reach to cloud-based applications and services.

There are several ways to achieve this integration:

  1. Federation Servers: Federation servers, such as Active Directory Federation Services (AD FS), enable organizations to establish trust between their on-premises AD and cloud-based IAM solutions. AD FS acts as the identity provider (IdP) for AD, issuing security tokens that can be used for authentication and authorization in the cloud environment. These security tokens can be consumed by the IAM solution, enabling SSO and access management for SaaS apps.
  2. SaaS-based Directories: Many IAM solutions, including Okta and Azure AD, offer directory services that can sync or federate with on-premises AD. These directory services act as a bridge between AD and the cloud-based IAM solution. User accounts and groups from AD can be synchronized with the SaaS-based directory, allowing for centralized management and authentication of cloud applications. Changes made in AD, such as user additions or updates, can be automatically reflected in the cloud-based IAM solution.

The synchronization or federation process typically involves the following steps:

  1. Establishing Trust: Trust needs to be established between the on-premises AD and the IAM solution. This involves configuring the necessary trust relationships, certificates, and other security settings.
  2. Directory Synchronization: User accounts, groups, and other relevant attributes from AD are synchronized with the cloud-based IAM solution. This ensures that the IAM solution has up-to-date information about users and their roles.
  3. Authentication and Authorization: The cloud-based IAM solution acts as the central authentication and authorization point for SaaS applications. When users attempt to access a SaaS app, they are redirected to the IAM solution for authentication. The IAM solution verifies the user’s credentials and, if successful, issues SSO tokens to grant access to the SaaS app.

By integrating AD with a cloud-based IAM solution, organizations can streamline user management, enhance security, and provide a seamless user experience across both on-premises and cloud environments.

Can an adversary move from a compromised Active Directory environment to access SaaS apps and cloud workloads?

Yes, if an adversary successfully compromises an Active Directory (AD) environment, they can potentially use that access to escalate their attack and gain unauthorized access to SaaS apps and cloud workloads. AD is a critical component of many organizations’ IT infrastructure, and compromising it can provide significant leverage for attackers.

Here are a few scenarios that illustrate how an adversary can leverage a compromised AD environment to access SaaS apps and cloud workloads:

  1. Credential Theft: An adversary with access to AD can attempt to steal user credentials stored in AD or intercept credentials during authentication processes. If successful, they can use these stolen credentials to authenticate themselves and gain unauthorized access to SaaS apps and cloud workloads.
  2. Privilege Escalation: AD is used to manage user accounts and permissions within an organization. If an adversary compromises AD, they can potentially escalate their privileges by modifying user permissions or creating new privileged accounts. With elevated privileges, they can access and manipulate SaaS apps and cloud workloads beyond their initial compromised entry point.
  3. Federation and SSO: Many organizations use federation and Single Sign-On (SSO) solutions to enable seamless access to SaaS apps. If the compromised AD environment is federated with the SaaS apps, the adversary may be able to exploit the trust established between AD and the SaaS apps to gain unauthorized access. This could involve manipulating federation settings, stealing SSO tokens, or exploiting vulnerabilities in the federation infrastructure.

Implementing Multi-Factor Authentication (MFA):

AD itself doesn’t have a way to discern between legitimate authentication and malicious one (as long as valid usernames and credentials were provided). This security gap could theoretically be addressed by adding Multi-Factor Authentication (MFA) to the authentication process. Unfortunately, the authentication protocols AD uses – NTLM and Kerberos – don’t natively support MFA step-up. 

The result is that the vast majority of access methods in an AD environment cannot have real-time protection against an attack that employs compromised credentials. For example, frequently used  CMD and PowerShell remote access tools like PsExec or Enter-PSSession cannot be protected with MFA, enabling attackers to abuse them for malicious access.

Implementing MFA strengthens the security of Active Directory by ensuring that even if passwords are compromised, an additional authentication factor is necessary for access. Organizations should consider implementing MFA for all user accounts, especially those with administrative privileges or access to sensitive information.

The Role of Auditing in Maintaining a Secure Environment:

Auditing is a critical component of Active Directory security. Enabling auditing settings allows organizations to track and monitor user activities, changes to security groups, and other critical events within the Active Directory infrastructure. By reviewing audit logs regularly, organizations can detect and respond to suspicious activities or potential security incidents promptly. Auditing provides valuable insights into unauthorized access attempts, policy violations, and potential insider threats, aiding in maintaining a secure environment and supporting incident response efforts.