Active Directory Security: A Guide to Protecting Your Core

Let’s be clear: in an enterprise environment, Active Directory isn’t just part of your network. It is your network.

It is the single source of truth for identity, authentication, and authorization. It controls every user, every computer, every group, and every permission. It holds the “keys to the kingdom.”

For this precise reason, Active Directory (AD) is the primary, high-value target for nearly every serious cyber-attacker.

A compromised Active Directory is not a minor security incident. It is a “game over” event. An attacker with Domain Admin rights doesn’t just steal data; they own your entire infrastructure. They can deploy ransomware to every workstation, create “Golden Tickets” to grant themselves permanent, invisible access, exfiltrate decades of data, and erase all evidence of their entry.

This isn’t just an IT disaster; it’s a business-ending catastrophe. It represents a total failure of your data security strategy and can lead Active Directoryto crippling penalties under new regulatory compliance in India.

The core problem is that Active Directory is, by default, built for functionality, not security. Many organizations are running on Active Directory environments set up 10 or 15 years ago, suffering from “configuration drift”, a decade of ad-hoc changes, staff turnover, and legacy protocols that have created a massive, undefended attack surface.

Protecting it is not optional. This is the definitive guide to modern Active Directory security.

Table of Contents

The Core Problem: Why Default Active Directory is a Ticking Clock

Attackers don’t “hack” Active Directory with zero-day exploits. They simply walk in through open doors left by common misconfigurations.

Their process is methodical:

Reconnaissance: They map your Active Directory structure, finding users, groups, and computers.
Foothold: They compromise a single low-level user (Tier 2) via a phishing email.
Privilege Escalation: This is the key. They use tools to find weaknesses, like a service account with a weak password, or a user who is unnecessarily in a local admin group, to move from a standard user to a Domain Admin.
Persistence: They create “Golden Tickets” or other backdoors. At this point, even if you find and remove them, they can get back in at will.

Your entire Active Directory security strategy must be built to break this attack chain, specifically at the “Privilege Escalation” step.

The Pillars of a Modern Active Directory Security Strategy

Securing Active Directory requires a multi-layered, defence-in-depth approach. You cannot just patch servers and hope for the best. This is the strategic framework our cyber security consulting services team implements to build a resilient AD.

Pillar 1: The Principle of Least Privilege (PoLP)

This is the absolute, non-negotiable foundation of all security. It means that no user, service, or computer has more access than the absolute minimum required to perform its job.

Stop Using Privileged Accounts: Your “Domain Admin” account should be treated like a nuclear launch code. It is only for “break glass” emergencies or core schema changes (e.g., adding a new Domain Controller). It must never be used for daily tasks like reading email, browsing the web, or managing user accounts.
Audit Privileged Groups: Regularly and relentlessly audit membership in groups like Domain Admins, Enterprise Admins, and Schema Admins. Every single member is a high-value target.
Delegate Granularly: Do not add users to broad, built-in groups like “Account Operators.” If your helpdesk team only needs to reset passwords for the “Sales” OU (Organizational Unit), create a custom security group, delegate only the “Reset Password” permission for only that OU, and add your helpdesk team to that new group.

Pillar 2: The Tiered Access Model

This is the single most effective structural defence you can build for Active Directory Security. It segments your assets to stop lateral movement, breaking the attacker’s path from a laptop to a Domain Controller.

It works by separating your assets into three logical tiers:

Tier 0: The core. This is the inner sanctum. It includes your Domain Controllers (DCs), Public Key Infrastructure (PKI) servers, ADFS servers, and all privileged accounts (Domain Admins, Enterprise Admins).
Tier 1: Enterprise servers. This includes your application servers, database servers, file servers, and the admin accounts for this tier.
Tier 2: End-user devices. This is everything else: all user workstations, laptops, and their accounts.

The Golden Rule: A lower tier can never initiate access to a higher tier.

A user on a Tier 2 workstation cannot RDP into a Tier 1 server.
An admin of a Tier 1 server cannot log into a Tier 0 Domain Controller.

This model is a game-changer. When an attacker phishes a Tier 2 user, they are stuck in Tier 2. They cannot use that user’s credentials to jump to a server. They cannot scan the network and find a path to a DC. This model starves them of escalation paths. Implementing this is a core service of top-tier network security firms.

Pillar 3: Harden the Crown Jewels (Domain Controllers)

Your Domain Controllers are your most critical assets. They must be treated as sacred.

Physical & Network Isolation: DCs must be on a highly restricted network segment (VLAN). Firewall rules must be strict: only allow required Active Directory ports (like Kerberos, LDAP, DNS) and only from specific, necessary sources. All other traffic should be denied.
Privileged Access Workstations (PAWs): This is a key Active Directory Security best practice. No one, not even a Domain Admin, should ever log into a Domain Controller from a standard workstation. All Tier 0 administration must be done from a separate, hardened, locked-down machine called a PAW. This device has no email, no web browser, and no office tools. It is used for nothing but Tier 0 admin.
Aggressive Patching: Your DCs must be on the fastest, most aggressive patching schedule you have. A “Patch Tuesday” vulnerability on a DC is a critical emergency.
Disable Legacy Protocols: Disable outdated, insecure protocols on your DCs, especially NTLMv1, SSL 2.0/3.0, and TLS 1.0/1.1. Enforce SMB signing to prevent man-in-the-middle attacks.

Pillar 4: Credential & Service Account Hygiene

This is where most attacks find their foothold.

Implement LAPS: The Local Administrator Password Solution (LAPS) is a free, essential Microsoft tool. It randomizes the local administrator password on every single workstation and server, storing the new, complex password securely in AD. This instantly neutralizes most “Pass-the-Hash” attacks, as the attacker can no longer use a single stolen local admin hash to move from machine to machine.
Secure Service Accounts: Standard service accounts (e.g., svc_sql) are a massive vulnerability. Their passwords are often simple and never changed.
- Move to gMSAs: Where possible, migrate to Group Managed Service Accounts (gMSAs). These are a special type of Active Directory account where the password is automatically managed, rotated, and secured by Active Directory itself.
- Audit Non-gMSAs: For all remaining service accounts, enforce 25+ character complex passwords, apply least privilege, and audit their permissions relentlessly.
Block “Kerberoasting”: This is an attack where a user requests a service ticket (TGS) for an account and cracks its password offline. The fix is simple: ensure all service accounts have long, complex, unguessable passwords.

Pillar 5: Assume Breach: Monitoring, Auditing, and Detection

Prevention is vital, but detection is critical. You must assume an attacker is already inside and be looking for them.

Enable Advanced Audit Policies: You cannot detect what you do not log. Ship your DC security logs to a SIEM (Security Information and Event Management) platform.
Create High-Fidelity Alerts: Your security team must be alerted immediately for:
- Event ID 4728, 4732, 4756: A user was added to a privileged group (Domain Admins, Enterprise Admins, etc.). This is a P0, “wake someone up” alert.
- Event ID 4625 (mass failures): A high volume of failed logons (brute force).
- Event ID 5136: A critical directory service object was modified (e.g., GPO changes).
Deploy Deception Tech: This is an advanced but powerful tactic. Create a “honeypot” user. Give it a tempting name like SQL_Admin_Backup and add it to the “Domain Admins” group description (but not the group itself). Set an alert that triggers if any activity (even a logon attempt) ever touches this account. Since no legitimate user should ever touch it, any alert is a high-confidence sign of an intruder.

Your Active Directory Security is Only as Strong as Your Last Audit

Active Directory is too complex and too critical to be a “set it and forget it” system. The attack landscape evolves daily.

You cannot protect against threats you cannot see. The only way to know if your defences work is to have them tested by experts.

This is where Ascella Infosec’s role as a leading vapt service provider becomes critical. Our Active Directory Security Assessment is not a simple vulnerability scan. As one of the top penetration testing companies in India, our expert red teams mimic the exact TTPs (Tactics, Techniques, and Procedures) of real-world attackers.

We will find the privilege escalation paths. We will identify the weak service accounts, the misconfigured GPOs, and the gaps in your Tiered Access Model.

Our IT security services team doesn’t just deliver a report of problems; we provide a prioritized, actionable roadmap to remediation. We help you build a resilient, hardened Active Directory environment that can withstand modern attacks.

Don’t wait for a “game over” event. Protect your core. Contact Ascella Infosec today for a comprehensive Active Directory Security review.