This website uses cookies to ensure you get the best experience on our website. Learn more
Top Active Directory security best practices for 2025
Table of Contents
(Last updated on May 22, 2025)
Active Directory (AD) remains the beating heart of most enterprise networks. But its this sheer ubiquity also makes it an irresistible target for modern attackers. In 2025, threat actors are no longer blasting blindly with mass phishing campaigns; they’re leveraging advanced credential-stealing techniques, abusing legacy protocols, and exploiting misconfigurations in hybrid environments to move laterally and achieve persistent footholds. With average attacker dwell times still measured in days, there’s zero room for complacency: every default setting you leave unaddressed, every weak service account password, and every unaudited GPO link is an invitation for compromise.
In this guide, you’ll find practical, expert-tested strategies for locking down every layer of your Active Directory estate. We’ll walk you through a 2025-caliber threat overview, Zero Trust-aligned controls, and hybrid-friendly hardening steps that cover on-prem DCs, 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, you’ll come away with clear, actionable steps—from enabling LDAP signing to orchestrating red-team simulations—so you can turn your directory into a fortress, not a gateway. The Active Directory security best practices provided below address security vulnerabilities in your organization, and serve as barriers for attackers.
2025 Active Directory threat landscape
As race through 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, so you can harden every potential entry point accordingly.
Understand Active Directory attacks
While Active Directory is designed with security in mind, its possession of the crown jewels makes it an attractive target for hackers. Their strategy is methodical – find an initial entry point, such as weak or compromised password. They they may try to escalate privileges to gain administration rights (even with basic access, attackers can escalate privileges and obtain administrator access in less than 72 hours). From there, the goal could be anything from stealing sensitive data to deploying ransomware.
As attacks get more sophisticated, thanks to automated tools, poor Active Directory hygiene can put your organization at risk. It’s important to stay on top of the most common Active Directory attack paths and how to remediate them.
Implement Zero Trust for Active Directory
If there’s one shift that separates effective defenders from the rest, it’s moving from perimeter defense to Zero Trust. And that principle applies just as much inside your AD environment. Start by micro-segmenting your domain controllers and critical servers so that each authentication or replication request crosses a defined network boundary. Layer on Conditional Access policies to require MFA for any user or service connecting to your AD admin tools, and set up continuous device and user risk evaluations so that every login attempt is scored in real time. 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.
Have 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 are not always interested in gathering data within a day, instead they could monitor data over a period of time. The mean number of days that an attacker resides within a victim’s network before detection is 200+ days.
A zero trust position entails applying additional controls around Active Directory. A real-time monitoring system along with alerting is an important part of early detection. Cataloging past activity will provide an easy comparison of current state and past state. Interestingly, 66% of breach victims had sufficient evidence within their logs to discover the breach. Finally, regular password changes can help protect your system from users who tend to reuse passwords – if their password is compromised elsewhere.
Enforce the principle of least privilege
Administrator privileges should only be granted to users performing tasks that span across Active Directory domains, or activities that require elevated permissions. To ensure accountability and move beyond a single point of failure, each administrator should have their own admin account – as opposed to a shared generic account with full rights. Furthermore, each administrator should have a separate user account, for day-to-day activities. For maximum security, a physical machine locked down to access only the internal server should be used for administrator tasks. For low-level activities, a virtual machine inside the physical machine can be granted outside access, without access to the host operating system that contains the elevated access.
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. Custom delegation groups should be in place to set privileges at the lowest level required for their responsibility. For example, common helpdesk tasks, such as unlocking accounts, and resetting passwords, do not require full control over an Organizational Unit.
Interested to know if you have any stale admin accounts lurking in your AD? Download our free tool and run a read-only scan with Specops Password Auditor.
Secure your Service Accounts
By ensuring service accounts only have the minimal privileges they need, leveraging Managed Service Accounts (MSAs) and Group MSAs for automatic, complex password rotation, and deploying LAPS for local-admin credentials, you eliminate hard-coded secrets and sharply reduce lateral-movement opportunities. Enforce robust, lengthy password policies, ban interactive logins, and place all service accounts in dedicated OUs governed by narrowly scoped GPOs to streamline monitoring. Pair this with regular audits to find and disable stale or orphaned accounts, strict segregation of account roles to limit blast radius, and forwarding of Security, DS Access, and Kerberos logs into your SIEM for real-time alerts on unusual activity. 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.
Check out our full ten best practices for securing service accounts here.
Harden Group Policy Objects & OU Design
A sprawling OU structure and broadly linked GPOs often lead to configuration drift and unintended exposures. Start by organizing your directory into trust-based tiers—keep Tier-0 assets (domain controllers, privileged workstations) in isolated OUs, separate from Tier-1 and Tier-2 objects. When you build Group Policy Objects, scope each GPO narrowly to the specific OU it serves rather than linking “at the domain root” by default. Store your ADMX/ADML central store under tight NTFS ACLs and only publish signed ADMX files to prevent 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. This approach reduces blast radius and ensures every policy change is fully tracked.
Enforce LDAPS, LDAP Signing & Channel Binding
By default, LDAP binds over unencrypted port 389—an attacker on the network can intercept credentials or even manipulate responses. To lock this down, disable TCP/389 on all domain controllers and in your perimeter firewall. Then, enforce LDAP signing via Group Policy (“Require signing”), which adds a cryptographic checksum to every 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 these settings out, monitor Windows Security event IDs 2886 (channel binding compliance) and 8217 (insecure bind attempts) to confirm that every client and application has moved to LDAPS (port 636) and is honoring your signing requirements.
Harden Active Directory Certificate Services (AD CS)
An improperly configured PKI becomes a single point of failure for all your Kerberos, S/MIME and other certificate-based services. Mitigate this by deploying a tiered CA hierarchy: keep your root CA offline in a secure vault and use a dedicated online issuing CA to service subordinate requests. 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. Finally, rotate your CA signing keys on a defined cadence (no less than every three years) and ensure your CDP/AIA endpoints are publicly reachable so clients can retrieve up-to-date CRLs and AIA chains without fail.
Implement a tiered admin model & delegation
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. Ensure 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.
Backup, disaster recovery & ransomware readiness
Even the best-hardened AD can fall victim to ransomware or accidental corruption; your security posture is only as strong as your recovery plan. 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” DC that lives off-network so you always have a clean build available. Twice a year, perform a full restore drill: bring that standby online, recover SYSVOL and NTDS.dit, and verify that authentication, Group Policy, and replication all function correctly. Don’t forget to manage your Directory Services Restore Mode (DSRM) account just like any other privileged credential—rotate it regularly via LAPS to ensure you never lose the keys to your own castle.
Advanced monitoring, SIEM Integration & attack simulation
Detection is your last line of defense, so make sure you’re collecting and analyzing every relevant signal from Active Directory. Forward Security, DS Access and Kerberos logs into your SIEM of choice, and build targeted alerts for telltale signs like Kerberoasting requests or golden-ticket forgeries. Layer 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: create automated runbooks that immediately disable compromised accounts, isolate infected hosts, and kick off forensic snapshots so your incident-response team can move faster than the adversary.
Be wary of insider threat
Employees, contractors, service providers, and other insiders are in an opportune position to compromise data. While the term Insider Threat often implies a deliberate wrongdoing, it can also encompass users that are careless or unaware of organizational security policies. Regardless of intent, there are some effective measures for stopping this threat. End-user training is an obvious start. Employees need to know what security policies are in place, and why. Next, you need a process for de-provisioning users that begins with immediate IT notification of any user changes. IT will have to disable/delete the relevant account, and remove the user from all groups and distribution lists. Temporary staff, contractors, interns, and visitors should have accounts with expiration dates. If temporary access to sensitive groups is required, you can assign temporary group memberships with automatic start and end dates.
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 (Free Tool) 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 best practices outlined in this document are certainly a good place to start if organizational security is keeping you up at night. Specops Password Policy is a tool that directly address some of the most critical AD security challenges and and integrates seamlessly with your existing environment. Book a free trial or demo today.
Specops Password Policy
- 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.
(Last updated on May 22, 2025)
Marcus White
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.