Active Directory (AD) remains the beating heart of most enterprise networks—and that central role makes it a prime target for modern attackers. In 2025, threat actors aren’t relying on generic phishing campaigns. Instead, they’re using advanced credential harvesting techniques, exploiting legacy protocols, and taking advantage of misconfigurations in hybrid environments to move laterally and establish long-term access.
With average attacker dwell times still measured in days, there’s no room for complacency. Every default setting left unchanged, every weak service account password, and every unaudited Group Policy link represents an open door for compromise.
This guide provides practical, expert-tested strategies for securing every layer of your Active Directory. You’ll get a 2025-ready threat overview, Zero Trust-aligned controls, and hybrid-compatible hardening steps that cover everything from on-premises domain controllers to Entra ID, service accounts, and disaster recovery.
Whether you’re just starting to mature your AD security posture or looking to validate an existing program, the best practices below will give you clear, actionable steps to transform your directory from a potential vulnerability into a resilient line of defense.
2025 Active Directory threat landscape
In 2025, Active Directory remains the prime gateway attackers target to gain a foothold in our environments. Gone are the days of indiscriminate phishing blasts; today’s adversaries favor precision credential theft, abusing legacy protocols like unsecured LDAP and weaponizing misconfigurations in hybrid setups. Median attacker dwell times are often measured in double-digit days, giving malicious actors plenty of room to map out trust relationships and harvest privileged credentials.
To stay ahead, we need a clear view of which attack vectors (whether Kerberoasting, Pass-the-Hash, or phishing-driven token theft) are trending, and apply the right Active Directory security best practices to harden every potential entry point accordingly.
Understand how Active Directory attacks work
Active Directory is built with security in mind, but because it controls access to critical systems and data, it’s a prime target for attackers. Their approach is often methodical: they start by gaining a foothold—usually through weak credentials or a compromised user account—and then work to escalate privileges. Alarmingly, even with low-level access, attackers can often achieve domain admin privileges in under 72 hours. From there, the goal could be anything from stealing sensitive data to deploying ransomware.
Password spraying: Attackers try common passwords against many accounts to avoid lockouts and find weak credentials.
Kerberoasting: Exploits service accounts by requesting service tickets and cracking them offline to retrieve plaintext passwords.
Pass-the-Hash: Uses hashed credentials from one system to authenticate on others without knowing the actual password.
Golden ticket attacks: Attackers forge Kerberos authentication tickets to impersonate any user, including domain admins.
DSync attacks: Attackers imitate the replication process of a domain controller by capturing credential hashes from the primary domain controller.
Privilege escalation: Exploits misconfigurations, such as over-permissioned accounts, to gain elevated rights.
Understanding these tactics is the first step in defending against them.
Active Directory security best practices
The following best practices are designed to help you reduce risk, close common gaps, and build a stronger, more resilient Active Directory—whether you manage a traditional on-prem deployment, a hybrid setup with Entra ID, or anything in between.
Here’s an overview of the top 12 Active Directory security best practices to implement, followed by a detailed breakdown of each with actionable steps to take:
Let’s take a closer look at each of these tips and the steps you can take to strengthen your Active Directory environment.
1. Implement Zero Trust for Active Directory
One of the most effective ways to secure Active Directory is to adopt a Zero Trust model, shifting from traditional perimeter-based defenses to a “never trust, always verify” approach.
Here’s how you can apply Zero Trust principles in your AD environment:
Micro-segment domain controllers and critical servers: Isolate high-value assets so that every authentication or replication request must cross a clearly defined security boundary.
Enforce Conditional Access with MFA: Require multi-factor authentication for all users and services accessing AD administrative tools—especially privileged accounts.
Evaluate risk continuously: Use tools that assess user and device risk in real time. Monitor behavioral signals (e.g. geolocation, device health, login patterns) to dynamically adjust access decisions.
With True Zero Trust, no session is implicitly trusted (even if the user is on-premises) so you’ll catch anomalous logins, lateral-movement attempts, and privilege escalations before they blossom into full-blown breaches.
2. Adopt an Assume Breach mindset for Active Directory
Organizations should assume attackers can get in, or they have already gotten in—it’s not a question of if, but how long. Hackers often play the long game, quietly monitoring and collecting information over weeks or months. In fact, the mean number of days that an attacker resides within a victim’s network before detection is over 200 days.
To protect your AD environment under this assumption, it’s essential to build layers of detection and resilience:
Implement real-time monitoring and alerting: Early detection tools can surface suspicious behavior before it escalates.
Log and baseline AD activity: Maintain comprehensive logs and create behavioral baselines so you can quickly spot deviations. Interestingly, 66% of breach victims had sufficient evidence within their logs to discover the breach.
Enforce regular password changes: These can help protect your system from users who tend to reuse passwords if their password is compromised elsewhere.
3. Enforce the principle of least privilege
Administrator privileges should only be granted to users who require them for specific tasks that span Active Directory domains or involve actions needing elevated permissions. To ensure accountability and reduce the risk of a single point of failure, every administrator should have a dedicated admin account— as opposed to a shared generic account with full rights. In addition, administrators should use a separate standard user account for daily, non-administrative tasks.
For maximum security, administrator tasks should be performed on a physically secured machine that is locked down and restricted to internal server access only. For general or low-risk activities requiring internet access, a virtual machine can be hosted within the physical machine, with strict separation to prevent any interaction with the host operating system that holds elevated privileges.
Finally, watch out for any stale admin accounts as they can be used to access resources without being noticed. One way of handling administrator privileges is through delegation. Rather than assigning full control, define custom delegation groups that grant only the minimum permissions needed for specific responsibilities. For example, common helpdesk tasks, such as unlocking accounts, and resetting passwords, do not require full control over an Organizational Unit.
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4. Secure your Service Accounts
Service accounts are often overlooked in security planning, yet they can become prime targets for attackers if misconfigured. To minimize risk, service accounts should be tightly controlled, monitored, and regularly audited.
Key best practices include:
Apply the principle of least privilege: Grant service accounts only the permissions they absolutely need to function, and nothing more.
Leverage Managed Service Accounts (MSAs) and Group MSAs: These accounts support automatic password rotation with complex, non-human-readable credentials, eliminating hard-coded passwords.
Deploy Local Administrator Password Solution (LAPS): LAPS automatically manages and rotates local administrator passwords on domain-joined machines, reducing the risk of lateral movement.
Enforce robust password policies: Use long, complex passwords and disable password expiration where rotation is automated.
Ban interactive logins: Service accounts should never be used for interactive logins; this reduces their exposure to compromise.
Place service accounts in dedicated Organizational Units (OUs): These should be governed by narrowly scoped Group Policy Objects (GPOs) for precise control and easier auditing.
Audit and clean up regularly: Identify and disable stale, unused, or orphaned service accounts that could be exploited.
Segregate service account roles: Avoid role overlap to limit the blast radius if one account is compromised.
Forward critical logs to your SIEM: Monitor Security, Directory Services Access, and Kerberos logs for unusual behavior and configure real-time alerts.
Rounding out your defense, add MFA where feasible, control vendor access through intermediary jump hosts, and conduct periodic reviews of service-account dependencies and permissions to keep your environment continuously hardened.
Not all administrator accounts are created equal, and you should never use your highest-privilege account for everyday tasks. Establish a clear three-tier model:
Tier-0 covers the domain controllers, enterprise admins and any AD-CS roles.
Tier-1 includes server and application admins.
Tier-2 is reserved for workstation and local-admin rights.
Make sure Tier-0 workstations have no Internet or email access, while Tier-2 machines cannot request domain-level changes. To assign day-to-day duties, use the AD “Delegation of Control Wizard” to grant only the specific permissions that each team needs, and no more.
Review these delegations every quarter, revoking any stale or unused rights to keep your attack surface as small and well-defined as possible.
6. Harden Group Policy Objects & OU Design
A sprawling OU structure and broadly linked GPOs can lead to configuration drift and unintended exposures. To prevent this, begin by structuring your Active Directory environment into trust-based tiers. Keep Tier-0 assets—such as domain controllers and privileged admin workstations—in isolated Organizational Units (OUs), completely separate from Tier-1 and Tier-2 assets.
When creating Group Policy Objects (GPOs), avoid linking them at the domain root. Instead, scope each GPO specifically to the OU it is intended to manage, ensuring policies are targeted and easier to audit. For added integrity, store your ADMX and ADML files in a centralized policy definitions store that is protected with strict NTFS access controls, and only publish signed ADMX templates to guard against unauthorized edits.
Finally, enable auditing for GPO changes (under the DS Access → Audit GPO Change sub-category) so you can trace who modified which policy and when. By tightening control over both OU structure and GPO deployment, you reduce the blast radius of misconfigurations and ensure every policy change is fully tracked.
7. Enforce LDAPS, LDAP Signing & Channel Binding
By default, LDAP binds over unencrypted port 389, leaving credentials and queries exposed to interception or tampering by attackers on the network. To secure LDAP traffic, start by disabling TCP/389 on all domain controllers and blocking it at the perimeter firewall to prevent unencrypted binds.
Next, enforce LDAP signing via Group Policy by enabling the “Require signing” setting. This adds a cryptographic checksum to each bind request, ensuring data integrity. For an even higher level of assurance, enable Channel Binding Tokens (CBT) so clients must verify the TLS session’s unique fingerprint before each bind.
As you roll out these protections, monitor compliance using:
Event ID 2886 – Indicates whether clients support and are using channel binding.
Event ID 8217 – Flags insecure or unsigned LDAP bind attempts that may require remediation.
This will confirm that every client and application has moved to LDAPS (port 636) and is honoring your signing requirements. With these controls in place, you significantly reduce the risk of credential exposure and ensure LDAP communications are both encrypted and tamper-proof.
8. Harden Active Directory Certificate Services (AD CS)
An improperly configured Public Key Infrastructure (PKI) can quickly become a single point of failure for all your Kerberos, S/MIME and other certificate-based services. To reduce this risk, begin by deploying a tiered Certificate Authority (CA) hierarchy. Keep your root CA offline in a secure vault while a separate, dedicated issuing CA handles certificate requests from subordinate entities.
Additionally, you should take the following steps:
Lock down “Enroll” permissions on certificate templates so only designated hosts and service accounts may request certificates.
Enable auditing for all CA-related events (Event IDs 513–515) so that any unauthorized template changes or revocations immediately trigger alerts.
Rotate your CA signing keys on a defined cadence (no less than every three years).
Ensure your CDP/AIA endpoints are publicly reachable so clients can retrieve up-to-date CRLs and AIA chains without fail.
Even the best-hardened AD can fall victim to ransomware or accidental corruption; your security posture is only as strong as your recovery plan. To prepare effectively:
Take daily system-state backups of every domain controller, capturing both the NTDS.dit database and the SYSVOL share.
Maintain at least one “cold standby” domain controller that remains off-network, providing a clean, isolated build for emergency recovery.
Conduct a full restore drill twice a year: bring the standby DC online, recover SYSVOL and NTDS.dit, and verify that authentication, Group Policy, and replication all function correctly.
Manage your Directory Services Restore Mode (DSRM) account with the same rigor as any privileged credential—rotate it regularly via LAPS to ensure you never lose the keys to your own castle.
By following these steps, you strengthen your organization’s ability to recover rapidly from ransomware attacks or failures, minimizing downtime and data loss.
Detection is your last line of defense, so make sure you’re collecting and analyzing every relevant signal from Active Directory. Forward Security, Directory Services Access, and Kerberos logs into your SIEM of choice to centralize data and create targeted alerts for telltale signs like Kerberoasting requests or golden-ticket forgeries
Enhance your visibility by layering on Microsoft Defender for Identity (formerly ATA) or a similar behavioral analytics tool to spot lateral-movement patterns in real time. Complement these controls by running quarterly red-team exercises using tools like BloodHound to simulate an attacker’s journey through your environment.
Finally, codify your response by creating automated runbooks that:
Immediately disable compromised accounts
Isolate infected hosts
Kick off forensic data collection and snapshots
This automation enables your incident response team to act faster than adversaries, minimizing damage and recovery time.
11. Be wary of insider threats
Employees, contractors, service providers, and other insiders are uniquely positioned to compromise sensitive data. While the term “insider threat” implies a deliberate wrongdoing, it also includes users who are simply careless or unaware of security policies. Regardless of intent, the impact can be severe, and proactive controls are essential.
To mitigate insider threats:
Provide regular end-user training so employees understand what security policies are in place, and why.
Establish a clear offboarding process that begins with immediate IT notification of any user changes. IT must promptly disable or delete the account, and remove the user from all groups and distribution lists.
Assign expiration dates to temporary accounts for contractors, interns, and visitors to ensure they don’t retain access longer than necessary.
Assign temporary group memberships with automatic start and end times when short-term access to sensitive resources is needed. This prevents privilege creep and means access is automatically revoked.
12. Monitor passwords for compromise
Many of the recent data breaches are the direct result of compromised passwords. Unfortunately, the built-in Active Directory policies don’t stop users from making poor password choices. That’s why we recommend auditing existing passwords to check for vulnerabilities.
Specops Password Auditor is our free, read-only tool that detects security weaknesses specifically related to password settings. By scanning your Active Directory, the tool collects and displays multiple interactive reports containing user and password policy information. The Breached Passwords report finds user accounts with passwords that are known to be leaked. The account in this list should be prompted to change their password.
Secure your Active Directory with Specops Password Policy
Active Directory security is a moving target, and while the periodic security audit will ensure that it is being properly managed, keeping an eye on daily changes is just as important. The Active Directory security best practices outlined in this article are certainly a good place to start if organizational security is keeping you up at night.
To further strengthen your defenses, consider Specops Password Policy. It directly addresses some of the most critical AD security challenges and integrates smoothly into your existing infrastructure. Book a free trial or demo today to see how it can support your organization’s security goals.
How Specops Password Policy helps ensure Active Directory security best practices
Enforce modern complexity rules (passphrases, banned lists, regex-based requirements) to prevent weak or reused credentials.
Block known compromised passwords by tapping into global breach archives—stopping attackers before they even log in.
Delegate policy changes through a friendly web console, with full audit logging of who changed what and when.
Continuously check all AD accounts against a growing database of over 4 billion breached credentials (NT-hash matching), alerting you if a user’s password is flagged as breached
Automate forced resets or self-service challenges for impacted users—dramatically reducing your mean time to remediation.
Continuously block 4 billion+ compromised passwords in your Active Directory
Marcus is a Specops cybersecurity specialist based in the UK, with 8+ years experience in the tech and cyber sectors. He writes about authentication, password security, password management, and compliance.