Designing AD for Zero Trust (practical first steps) means reshaping your on-premises Active Directory (AD) so that every access request is explicitly verified, least-privileged, and resilient to compromise. Zero Trust is a security model that assumes no implicit trust—inside or outside your network—and continuously validates identity, device health, and context. This guide gives you a clear, actionable path to begin that journey in AD without boiling the ocean.
1) Introduction & Context
Designing AD for Zero Trust (practical first steps) is a repeatable process to modernize identity security where it matters most—your domain controllers, privileged groups, and critical workloads. You would follow this process when:
- Your organization is beginning a Zero Trust program and AD remains the primary identity provider.
- You must reduce ransomware blast radius, lateral movement, and credential abuse.
- You want quick, high-impact controls that do not require a full re-architecture on day one.
Outcome: an AD environment with explicit verification, segmented privilege, hardened protocols, and measurable controls you can iterate.
If you want a refresher on how Windows authentication mechanics influence blast radius (and why tightening “legacy” auth matters so much), see NTLM and Kerberos authentication protocols explained.
2) Preconditions & Setup
Prerequisites, tools, skills:
- Executive sponsorship & change control. You will modify identity policies that affect many systems.
- A test lab mirroring production OUs, GPOs, and a subset of apps.
- Recent backups of AD (system state), GPOs, and a DC snapshot.
- Health checks: dcdiag, repadmin /replsum, DNS integrity, time sync.
- Tooling: RSAT, Group Policy Management Console (GPMC), Event Viewer, PowerShell (AD, GroupPolicy, PSDesiredStateConfiguration), Sysinternals, LAPS (Local Administrator Password Solution) or Windows LAPS, and a secrets vault (your preferred enterprise secrets manager). (If you need a quick GPMC primer: Managing GPOs with Group Policy Management Console.)
- Documentation of critical apps using LDAP/LDAPS, NTLM/Kerberos, or service accounts.
Environmental factors to address upfront:
- Align with PKI if using smartcards, certificates, or LDAPS hardening.
- Identify legacy dependencies (old NTLM or unsigned LDAP binds). If you’re still mapping LDAP touchpoints, this can help: Integrating AD with LDAP.
- Define a maintenance window and a rollback plan for each control.
3) Core Principles Guiding the Process
- Verify explicitly. Every request must prove user, device, and context; do not trust network location.
- Least privilege. Give only what is needed, only when needed, and remove when done.
- Assume breach. Design like an attacker is already on a workstation; constrain lateral movement and credential theft impact.
- Segment by risk. Separate Tier-0 (domain controllers, PKI), Tier-1 (servers), and Tier-2 (workstations).
- Continuously evaluate. Controls must be observable, measured, and iterated.
Understanding these principles helps you adapt when conditions change—for example, when a legacy app cannot meet a control, you isolate it rather than exempt the whole domain.
For a practical “delegation-first” mindset that pairs well with Zero Trust (and avoids accidental domain-wide privilege), see How to delegate OU permissions with minimal risk.
4) Step-by-Step Execution
Step 1: Establish an AD Zero Trust Baseline
What to do
- Inventory privileged groups (Domain Admins, Enterprise Admins, Schema Admins, Backup Operators, Account Operators, Print Operators) and all nested memberships.
- Enumerate all service accounts, their SPNs, password ages, and interactive logon rights.
- Map protocol usage (NTLMv1/v2, Kerberos, LDAP/LDAPS, SMB signing).
- Capture DC health metrics and replication status.
- Record admin workflows: where admins log on, jump hosts, and toolsets used.
Why it matters
You cannot reduce risk you cannot see. Baselines reveal toxic combinations: standing Domain Admins, interactive logons on Tier-2 devices, or NTLM used by critical apps.
Pro tips
- Use PowerShell to extract group nesting and stale accounts; export to CSV and review with security and app owners.
- Tag each finding with “Tier-0/Tier-1/Tier-2” to prioritize. If nested group paths are a blind spot, use this as a reference: Auditing nested group memberships.
Step 2: Tier Your Assets and Identities
What to do
- Implement a 3-Tier model:
- Tier-0: DCs, PKI, identity systems, federation, directory synchronization.
- Tier-1: Server workloads and management tooling.
- Tier-2: User workstations and VDI.
- Create separate admin accounts per tier (no cross-tier logon).
- Build Privileged Access Workstations (PAWs) for Tier-0/1 admins.
Why it matters
Tiering prevents credential theft on a workstation from compromising domain controllers. It enforces natural blast-radius boundaries.
Pro tips
- Use GPO logon restrictions to enforce where privileged accounts can authenticate.
- Consider dedicated management forests or hardened jump servers for Tier-0.
- If you’re redesigning OU structure to make tiering and delegation durable (and audit-friendly), see How to design OU for rock-solid RBAC.
Tiering at a glance
| Tier | Examples | Who can log on | Must-have controls |
|---|---|---|---|
| Tier-0 | DCs, PKI, IdP | Tier-0 admins only | PAWs, MFA, no internet, code signing |
| Tier-1 | Servers, mgmt tools | Tier-1 admins | Just-in-Time access, RBAC, session isolation |
| Tier-2 | Workstations | End users | EDR, patching, attack surface reduction |
Step 3: Enforce Strong Authentication and MFA
What to do
- Require MFA for all privileged operations and remote admin paths.
- Enable smartcard/credential guard or phishing-resistant factors where feasible.
- Enforce Kerberos preauthentication and disable anonymous binds.
- For LDAPS, use valid server certificates and require signing.
Why it matters
Zero Trust depends on robust, verifiable signals. MFA breaks many commodity attack chains.
Pro tips
- Start with Tier-0 and Tier-1. Expand to break-glass accounts with strict storage and periodic validation.
- Audit RDP, WinRM, and PSRemoting to ensure MFA or equivalent strong auth paths. (If you’re revisiting the fundamentals of how auth and authorization differ in AD, this is handy: Authentication vs authorization process.)
Step 4: Minimize Standing Privilege (JIT + JEA)
What to do
- Remove permanent membership in Domain Admins and other powerful groups.
- Implement Just-in-Time (JIT) access: grant admin roles only for the task window.
- Use Just Enough Administration (JEA) to constrain what privileged sessions can do.
- Introduce role-based access control (RBAC) for common tasks.
Why it matters
An attacker cannot reuse privileges that do not exist outside a short window. Reducing “standing” rights sharply limits impact.
Pro tips
- Time-box elevation to hours, not days.
- Log all elevations; alert on elevations outside change windows.
- If you use Entra / Azure AD, JIT patterns often map cleanly to PIM workflows—useful for hybrid programs: How to manage privileged access (PIM).
Step 5: Harden Protocols and Domain Controllers
What to do
- Disable LM/NTLMv1; restrict NTLM; require SMB signing; prefer Kerberos.
- Enforce LDAP signing and channel binding; require LDAPS for applications.
- Harden DCs: minimal roles, reduced attack surface (disable unused services), and audited local rights.
- Keep DCs fully patched; isolate internet and email access from Tier-0.
Why it matters
Credential relay, downgrade, and replay attacks thrive on weak protocol settings. DCs must be the hardest target in your environment.
Pro tips
- Test LDAP signing in the lab before production; inventory apps that still use simple binds.
- Monitor for NTLM traffic spikes; they often reveal legacy systems.
- If your team needs shared language around NTLM vs Kerberos tradeoffs while planning restrictions, link this internally: NTLM and Kerberos protocols explained.
Step 6: Segment Administration and Sessions
What to do
- Enforce no admin logon to Tier-2 devices with Tier-0/1 credentials.
- Use PAWs or hardened jump hosts with strict inbound/outbound rules.
- Isolate management networks using firewall rules and admin-only VLANs.
Why it matters
Most compromises begin on endpoints. Session isolation prevents stolen tokens or credentials from reaching high-value targets.
Pro tips
- Block copy/paste and internet from PAWs; log keystrokes and sessions for Tier-0 operations.
- Tag management subnets; apply additional IDS/IPS scrutiny.
Step 7: Secure Service Accounts and Secrets
What to do
- Replace traditional service accounts with gMSA (Group Managed Service Accounts) where possible.
- Rotate all remaining service account passwords frequently; remove interactive logon rights.
- Store secrets in a vault; remove passwords from scripts and GPO preferences.
- Validate SPNs to prevent Kerberoasting opportunities.
Why it matters
Service accounts often hold excessive privilege and never change passwords—prime targets for attackers.
Pro tips
- Use constrained delegation rather than unconstrained; audit TrustedToAuthForDelegation.
- Alert on AS-REP roasting indicators (accounts without preauth).
- For a practical gMSA starting point (and why it reduces risk operationally), see: Configure gMSA (step-by-step).
Step 8: Govern Endpoints and GPOs
What to do
- Standardize baseline GPOs: credential guard, LSASS protection, PowerShell logging, device control, and attack surface reduction rules.
- Remove Local Admin rights for users; deploy Windows LAPS to randomize local passwords.
- Sign and control logon scripts; eliminate legacy startup scripts with embedded secrets.
Why it matters
Endpoints are the largest attack surface. Strong baselines reduce the chance a compromised workstation can pivot.
Pro tips
- Back up and version GPOs; document settings in readable change logs.
- Use WMI filters and security groups to target GPOs by tier (see: GPO security filtering and WMI filtering).
- If you’re rolling out LAPS for the first time (or standardizing it domain-wide), this walkthrough helps: How to install and set up Microsoft LAPS.
Step 9: Monitor, Log, and Continuously Verify
What to do
- Forward DC security logs to a SIEM. Monitor admin group changes, elevation events, and authentication anomalies.
- Track KPIs: number of standing Domain Admins, NTLM traffic volume, MFA coverage, stale privileged accounts, and time-to-revoke elevated rights.
- Continuously validate configuration drift using scripts or desired state configuration.
Why it matters
Zero Trust is not a switch; it is a loop. You must observe, measure, and correct.
Pro tips
- Create detections for new SPNs, changes to GPOs linked to Tier-0 OUs, and failed LDAPS binds.
- Review KPIs monthly; publish a simple scorecard to executives.
5) Optimization & Troubleshooting
Mental models for refinement
- Tighten the loop: Measure → prioritize → fix → measure again. Start with Tier-0 indicators.
- Risk-weighted backlog: Rank work by blast radius reduction per engineering hour.
- Contracts over exceptions: When a legacy app needs NTLM, wrap it in a hardened enclave with compensating controls and an expiration date.
Detect and correct deviations
- Sudden spikes in NTLM → find new or misconfigured systems; push SMB signing and Kerberos first.
- Unauthorized privileged logons to Tier-2 → adjust logon GPOs and PAW policies.
- Frequent failed LDAPS binds → inspect certificates, CA chain, and channel binding.
When something breaks
- Revert the last GPO change; confirm replication; check time sync and PKI chain.
- Use targeted scoping: apply stricter policies first to pilot OUs before global rollout.
- Keep a tested rollback for protocol hardening (e.g., staged NTLM restrictions).
6) Common Pitfalls
- Big-bang hardening. Rolling every control at once causes outages; use phased deployment.
- Ignoring service accounts. They often hold the keys; prioritize gMSA adoption and rotation.
- Admin sprawl. Too many Domain Admins erode Zero Trust; move to JIT and RBAC.
- Protocol surprises. Enforcing LDAP signing without app inventory breaks line-of-business services.
- No PAWs. Mixing admin and daily browsing invites credential theft.
- Skipping measurement. Without KPIs, you cannot prove or sustain progress.
7) Final Checklist (Quick Reference)
- Back up AD and GPOs; validate DC health.
- Inventory privileged groups, service accounts, protocol usage.
- Implement 3-Tier model; create tier-scoped admin accounts.
- Deploy PAWs for Tier-0/1; enforce logon restrictions.
- Require MFA for privileged operations and remote admin.
- Remove standing Domain Admins; enable JIT/JEA and RBAC.
- Harden protocols: restrict NTLM, require SMB signing, enforce LDAP signing/LDAPS.
- Secure service accounts: gMSA, rotation, vaulting; fix SPNs and delegation.
- Standardize GPO baselines; remove local admin; deploy (Windows) LAPS.
- Centralize logs; define KPIs; iterate monthly.
Key Takeaways
- Start where risk peaks: Tier-0, privileges, protocols, and service accounts.
- Least privilege plus MFA stops most credential-based attacks.
- Session and tier isolation contain inevitable endpoint compromises.
- Continuous verification turns Zero Trust from a project into a practice.
- Measure relentlessly; improvement follows visibility.
FAQ
Q1: Does Zero Trust mean rebuilding AD from scratch?
No. Begin with targeted controls—tiering, MFA, protocol hardening—and iterate.
Q2: Can I keep NTLM for legacy apps?
Temporarily, in an isolated enclave with compensating controls and a deprecation plan.
Q3: How many Domain Admins should we have?
Aim for zero standing Domain Admins; use Just-in-Time elevation when needed.
Q4: Do I need a separate admin forest?
Not always. PAWs, JIT, and strict tiering often deliver most benefits without added complexity.
Q5: What breaks most often during hardening?
Apps relying on unsigned LDAP binds or legacy NTLM. Inventory first; pilot changes.
Q6: How do I prove progress to leadership?
Show MFA coverage, reduction in standing privilege, NTLM traffic decline, and time-to-revoke elevated access.