What is Active Directory Security? Risks and Best Practices

Active Directory (AD) is a Microsoft Windows service that stores, manages, and centralizes access controls for domains, applications, groups, user accounts, and endpoint devices. Originally developed to manage access rights just for Windows, Active Directory is now used to manage access rights for Linux and macOS systems. With more and more organizations managing IT operations from the cloud, Microsoft has also released Microsoft Entra ID, formerly Azure AD, a cloud-based version of Active Directory that provides network and identity access management for both cloud and traditional on-premises environments.

One reason Active Directory is so popular is its scalability. The directory service allows organizations to manage access controls and enforce security policies in a flexible, scalable manner for everything from groups of tens of thousands of users to a lone device accessing a network from a remote location. Unfortunately, due to the critical role Active Directory plays in authentication and authorization, it has also become a tempting target for attackers.

This blog post will explore the role of security in Active Directory, common attack methods, and how to protect your organization from potential breaches to your Active Directory instance.

Whether you’re using it on-premises, in the cloud, or in a hybrid environment, the security risks remain the same, and understanding what best practices to follow can help you proactively secure your Active Directory environment.

• Key components of Active Directory security
• Why is securing Active Directory important?
• What are common AD security risks?
• 5 Active Directory security best practices
• Gain visibility and control to improve Active Directory security

Key components of Active Directory security

To better understand the needs of AD security, it’s helpful to understand its structure. Active Directory uses the concept of domains, forests, and trees to organize access controls and streamline managing user and device accounts:

• A domain is a sub-structure within an Active Directory environment that houses objects on a network like users, computers, and groups within a common authentication database. Domains rely on specialized servers known as domain controllers (DCs) that consolidate storing and managing object information and user authentication requests in one place. Security groups, organizational units (OUs), and group policy objects (GPOs) are standard methods used at the domain level to streamline administrative tasks.
• A tree is a structured, tiered arrangement of one or more domains within Active Directory. In an enterprise network, numerous users and individual trees can consist of multiple domains or subdomains, all originating from a root domain. The root domain in Active Directory is the “root” of the tree structure and sets the standard for naming conventions across a forest.
• A forest is a collection of one or more domain trees that share schemas, configurations, and global catalogs, allowing for centralized management of multiple domains. Each forest also acts as a security boundary, which means that for objects in separate Active Directory forests to interact with one another, trust must be established by the administrators overseeing each respective forest. Without this trust, interaction between the objects across forests is not possible.

With this overview of the AD structure, you can see how managing Active Directory can become quite challenging and increasingly complex. Organizations must manage and maintain Active Directory to ensure that the right users, devices, and services have the appropriate levels of access because all it takes is one misconfiguration to hand attackers the keys to your IT kingdom.

Why is securing Active Directory important?

Active Directory is often described as the “keys to the IT kingdom” since it’s the central service used to store and manage access controls for every endpoint, application, and service that requires credentials. This also makes AD a prime target for attackers, whether their goal is to perpetrate a data breach, install malware, or engage in some other type of malicious behavior.

While Active Directory is a valuable service, reports show that half of organizations have experienced Active Directory cyberattacks. Unfortunately, when Active Directory is vulnerable, all user accounts and services it manages access privileges for are also at higher risk of compromise.

What are common AD security risks?

As the NSA and CISA determined, AD security incidents are often the result of misconfigurations stemming from poor cyber hygiene practices, including:

Using weak and default passwords

Using a weak password for the Active Directory administrator account or any other key account makes it easier for attackers to break in. Once inside, they can attempt to escalate privileges, create new accounts to gain more access, and even change permissions or delete accounts to halt operations by shutting employees out from business-critical services.

Additionally, using default passwords can eliminate time and guesswork for attackers, giving them speedy and likely undetectable access to valuable resources. Since Active Directory comes configured with default passwords set up by Microsoft, administrators should take the time to change default passwords for Active Directory and all their applications, services, and devices.

User accounts with incorrect privilege levels

Remember that user accounts inherit the privileges of their groups. Regularly reviewing access privileges can help ensure that Active Directory users are not being granted privileges beyond those necessary for their jobs simply because they belong to a certain group. For example, domain user accounts can add workstations by default, meaning attackers with these compromised credentials can add personal computers to more easily access your environment.

Another example of attackers leveraging AD accounts is Kerberoasting, which gets its name from Kerberos — an authentication protocol used by Windows to authenticate services on untrusted networks. Attackers first compromise a user account using phishing, keylogging, a memory scraping tool like Mimikatz, or some other technique to gain login access. Once logged in, the attacker looks for Active Directory service accounts with Service Principal Names (SPNs) enabled.

Service accounts are often targeted due to the elevated permissions granted to them, as organizations tend to set up these accounts with high-level domain privileges to ensure users have uninterrupted access to the resources they need. The attacker then requests tickets from the Kerberos Ticket Granting Service (TGS), which returns encrypted, hashed versions of the passwords for the accounts the attacker can extract and work offline to crack.

If successfully breached, the possibilities of what attackers can do in AD environments are endless — They can look for privilege escalation opportunities, which use one account to obtain more privileged access to other resources within the network. Attackers can also install ransomware that spreads quickly across the organization, wreak havoc on business operations by corrupting or stopping processes, and cause irreparable data loss.

The balance between enforcing policies to maintain AD security and ensuring that users have the necessary access to perform their duties is delicate. If not managed properly, this can lead to security gaps and IT compliance issues that make the organization vulnerable to security breaches.

Insufficient policy and patch management

Like all enterprise software, Active Directory needs to be updated occasionally to improve performance and fix recently discovered security vulnerabilities. Failing to patch Active Directory in a timely manner gives attackers the opportunity to attack the service using known exploits. It is also critical to ensure Windows Server operating systems and other software are up to date.

[Read also: The essential guide to slow patching: The reasons, risks, and remedies]

Conflicting Active Directory and local policies can also create complications. For example, if an endpoint is joined to a domain and receives a domain policy that contains the same policy setting that a local policy is trying to apply, the domain policy will take precedence, which can lead to management challenges.

Attackers often exploit misconfigurations to trick Active Directory into issuing fraudulent certifications or escalating the privileges granted to include administrative privileges. Like Kerberoasting, these attacks are difficult to detect since the actions appear to be issued legitimately, allowing attackers longer dwell time in environments and more opportunities to cause damage.

5 Active Directory security best practices

By following these AD security best practices, organizations can help keep Active Directory and all the domains, user accounts, and IT resources it controls more secure:

1. Embrace Zero Trust and multi-factor authentication (MFA)
   
   Zero-Trust security means that users and devices are afforded zero trust by default and are not trusted until verified. Users are granted access rights in compliance with the principle of least privilege only after verification. Applying the principle of least privilege when configuring access controls for accounts, whether for users or services, gives users the access privileges they need to do their jobs — and nothing more.
   
   For example, if a user needs read access to a finance application for their job, the principle of least privilege would mean they’re only given access to that specific application and not every business application to guarantee that attackers will have as little access as possible if they manage to take over the account.
   
   Multi-factor authentication is also essential to implementing Zero Trust. MFA requires anyone accessing an account to use a password and a secondary authentication method, such as a randomly generated numerical key delivered by text or email or an encrypted digital signature stored on a hardware key. Requiring multi-factor authentication can make it more difficult for attackers to gain access to AD using compromised user accounts.
2. Enforce strong password policies
   
   Even with MFA and Zero-Trust security models in place, they are not foolproof. Strict password policies remain a critical defense mechanism for bolstering Active Directory security and act as additional safeguards, ensuring that even if other security layers are compromised, the integrity of Active Directory remains intact.
   
   Many modern password policies require complex passwords containing upper- and lowercase letters, numbers, and symbols. Strong passwords should also be at least 12 characters long, though Microsoft recommends that 14 or more is even better. It’s best to use randomly generated passwords from password managers rather than passwords composed of common words with numbers and symbols thrown in. Additional types of password policies organizations can implement include password expirations, lockout policies, and blocking commonly used passwords known to be vulnerable.

A customer used the same local administrator password for all Windows endpoints. When an attacker gained access to one endpoint, they were able to move laterally and gain administrative privileges on all endpoints because of the shared password. This led to privilege escalation within the Active Directory Domain Services (AD DS) domain and a total domain compromise.

3. Reduce the attack surface with proper user account management
   
   Attack surfaces continue to expand as endpoints multiply and teams adopt multi-cloud strategies. With a compromised account, attackers can successfully move from one endpoint to another or use vulnerable network ports to conduct attacks, a process called lateral movement.
   
   By proactively monitoring endpoints, analyzing potential paths of attack, and understanding different user permissions and levels of account access, organizations can better harden Active Directory by improving security settings on user accounts to restrict movements should attackers gain access, minimizing the potential for security breaches.

[Read also: What is endpoint security? Benefits, types, and best practices]

Another opportunity to shrink the attack surface is promptly deleting accounts if a user, especially a user with a privileged account, leaves your organization or changes jobs. This can help eliminate the risk of attackers taking over or compromising unused accounts.

Limiting the number of domain admins in an Active Directory environment can also help minimize your attack surface. Since domain administrators have the power to create and configure access rights for accounts and are usually members of the administrator group on all domain controllers, the potential for a domain to be compromised increases as the number of users in privileged security groups grows.

4. Keep your systems patched, updated, and backed up
   
   If Active Directory goes down, users across the organization lose the ability to authenticate themselves. Setting up a backup server for your Active Directory domain can allow you to fall back and restore access privileges to ensure the continuation of daily business operations if your primary server has an outage or is compromised in a cyberattack. Establishing a formal recovery plan for your AD server and testing it regularly can also help you ensure everything works or will work properly when a security incident occurs.
   
   Another best practice is to keep all systems up to date and fix any security issues as soon as possible to lessen the risk of security breaches that could compromise the availability or integrity of Active Directory services. Through updates and effective patch management, organizations can also maintain compliance with industry or regulatory standards that require a certain level of security for sensitive data and systems.

The vast majority of successful cyberattacks could be thwarted by implementing a few fundamental security hygiene practices.

5. Use a layered security approach
   
   The harsh reality is no single cybersecurity solution can combat all modern threats. Instead, you can better protect your directory service by leveraging multiple security solutions and strategies to help address different attack vectors. For example, implementing firewalls, such as DNS or Windows firewalls, can help enhance Active Directory security by controlling both incoming and outgoing traffic, ensuring only essential traffic is permitted, and helping prevent unauthorized users from accessing your environment.
   
   You can also implement tools on your network to help detect Active Directory-focused attack types, such as brute force attacks against passwords. In a brute force attack, attackers use scripts to rapidly try many passwords to log into an account. The AD domain administrator password and accounts with privileged access are common targets for brute force attacks. If one of the random combinations succeeds, attackers gain access. To prevent this type of attack from succeeding, having controls that lock accounts after a few failed login attempts and alert that a brute force attack may be underway can help organizations better mitigate security incidents.
   
   It’s important to recognize that selecting the right Active Directory security solutions should be based on a clear understanding of your organization’s specific needs. Not only is their effectiveness contingent on the current threat landscape, but they must also align with your organization’s objectives, unique risks, regulatory requirements, and operational considerations. Performing a thorough business needs assessment and determining your cyber risk score are critical to implementing the most appropriate and powerful AD security strategies.

Gain visibility and control to improve Active Directory security

As these security risks and best practices show, fortifying Active Directory security is crucial for safeguarding your organization against attacks and a requirement for a comprehensive enterprise cyber defense strategy. It’s a type of security where the details matter, and simply granting a user the wrong set of access privileges could allow attackers access to your organization’s most valuable assets.

As adversaries evolve their strategies and techniques, IT, security, and operations teams must stay on top of emerging threats, follow AD security best practices, and have the right tools in place to prevent vulnerabilities. By using real-time monitoring, automating security tasks, and a unified set of solutions, organizations can more easily control the attack surface by ensuring access rights, security policies, and user account permissions work to defend against and not increase security risks.

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In a single platform, Tanium Converged Endpoint Management (XEM) helps organizations protect IT assets from unauthorized access, investigate suspicious activity, remediate threats, and fine-tune Active Directory and security efforts to reduce attack surfaces, bolstering an organization’s overall cyber defense.

Our risk and compliance solutions allow you to understand the administrative realm of your enterprise by visualizing and contextualizing access rights. Not only can the platform identify which user accounts, groups, and endpoints have privileged access in Active Directory environments, but it can also monitor for vulnerability and compliance gaps across every managed and unmanaged endpoint in your estate and prioritize areas for reducing administrative privileges, particularly for essential assets, to minimize the potential for attacks. Using Tanium, you can more easily determine whether the correct access rights have been granted and better manage permissions per user. If you determine a user doesn’t need administration rights, you can easily remove these permissions directly within the platform to lessen the risk of lateral movement.

Improving your ability to manage risk and compliance is also a key component of our vision for Autonomous Endpoint Management (AEM) — the next evolution of our XEM platform. It will combine pre-configured playbooks, seamless platform integrations, AI-driven insights, workflows, and the ability to automate remediations through real-time control and visibility to unify IT operations and security teams. You can schedule a free, personalized demo to learn how AEM at Tanium can provide unmatched operational efficiency and risk mitigation capabilities.