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Active Directory (AD) is vital for IT infrastructure. It manages identity and access for organizations. However, if attackers compromise AD, they can move through systems, escalate privileges, and even take control of a domain. That’s why securing and strengthening Active Directory is so important.

This blog outlines key security measures to protect your AD environment, with actionable insights covering authentication, access controls, domain controllers, lateral movement prevention, and security monitoring. 

Securing Authentication & Enforcing Strong Password Policies

A strong authentication framework ensures that only authorized users access sensitive resources. This section focuses on solidifying user authentication and password policies in AD. 

Enforce Strong Authentication Policies 

Strong authentication methods lower the risk of attacks using credentials. This includes threats like Pass-the-Hash and brute force. Critical approaches include the following:

• Enable Multi-Factor Authentication (MFA): Use MFA for privileged accounts. It adds extra security. MFA mitigates risks even if a password is compromised. 
• Use Certificate-Based Authentication: For high-risk users, like administrators, use certificate-based authentication. This boosts access security. 
• Restrict NTLM Authentication: NTLM is a weak authentication protocol vulnerable to Pass-the-Hash attacks. Use Group Policy Objects (GPOs) to restrict or disable NTLM where feasible. 

Strengthen Password Policies 

Weak or shared passwords significantly undermine organizational security. Enhancing password policies is non-negotiable. 

• Set Strong Password Rules: Require passwords to be at least 14 characters long. They should include uppercase, lowercase, numbers, and symbols for added complexity. For service accounts, utilize non-expiring passwords to prevent accidental lockouts. 
• Fine-Grained Password Policies (FGPP): Set up FGPP to apply specific password rules for different teams or groups. 
• Check for Compromised Passwords: Use Azure AD Password Protection to find and block compromised passwords. 

Effective authentication ensures your AD remains secure against unauthorized access.

Hardening Privileged Accounts & Access Controls 

Privileged accounts are top targets for cyberattacks. So, it’s crucial to limit their access and secure them as a key defense.

Implement Least Privilege Access (LPA) & Role-Based Access Control 

Excessive privileges pose a major attack vector. Here’s how to reduce exposure effectively:

• Limit Domain Admin Accounts: Reduce the number of users in the Domain Admins group to cut down on broad access. Restrict Domain Admin accounts to administrative tasks only. 
• Use Separate Accounts for Admins: Admins should have different accounts for everyday tasks and for special operations. 
• Restrict GPO Editing: Only allow trusted admins to edit Group Policy Objects (GPO). This helps prevent accidental or harmful changes. 

Implement a Tiered Admin Access Model 

A tiered model isolates different levels of administrative access to improve security posture. 

• Tier 0: Domain controllers, enterprise administrators, and other resources critical to AD integrity. 
• Tier 1: Application and server administrators with restricted access. 
• Tier 2: Workstation admins and helpdesk staff with limited privileges. 

This structured approach minimizes lateral movement risks. 

Secure Service Accounts 

Service accounts often have elevated permissions and are thus prime targets. 

• Use Group Managed Service Accounts (gMSAs): Switch from static passwords to gMSAs. This helps you avoid managing passwords manually. 
• Restrict Interactive Logins: Set up service accounts to stop interactive login attempts. This helps reduce credential misuse. 

Securing Domain Controllers & AD Infrastructure 

Domain controllers (DCs) are the lifeblood of your AD environment. Securing them is essential to maintaining AD integrity. 

Protect Domain Controllers (DCs) from Unauthorized Access 

Physical and logical security controls protect domain controllers from compromise. 

• Restrict Login Access: Only allow authorized personnel to log in to domain controllers. 
• Turn Off Unused Services: Disable services and protocols you don’t use, like old SMB and Telnet versions. 
• Enable BitLocker Encryption: Use BitLocker to protect your data on the disk. This helps keep it safe from theft or unauthorized access. 

Restrict Network Access to AD Services 

Controlling how domain controllers are accessed via the network reduces their attack surface. 

• Limit RDP access to DCs. Require multi-factor authentication for added security. 
• Set Firewall Rules: Limit LDAP and SMB protocols to only approved endpoints using the Windows Firewall. 
• – Use Jump Servers: Admins must access domain controllers via secure jump servers for special sessions. 

Enforce Secure LDAP (LDAPS) and Channel Binding 

Unsigned LDAP traffic opens vulnerabilities to man-in-the-middle attacks. 

• Disable Unsigned LDAP Connections: Require LDAPS for all directory queries. 
• Enable LDAP Channel Binding: This adds more security to LDAP connections. It helps make them stronger against attacks. 

Preventing Lateral Movement & Attack Persistence 

Preventing attackers from spreading laterally ensures breaches remain contained. 

Disable Unused and Legacy Protocols 

Older protocols increase your risk of credential theft and other security breaches. 

• Turn Off SMBv1, LLMNR, and NetBIOS: These old protocols are weak and can be easily attacked, like having credentials stolen. 
• Restrict PowerShell Remoting: Limit PowerShell remote access to authorized administrators only. 

Secure Kerberos Authentication 

Misconfigurations in Kerberos can lead to “Kerberoasting” attacks. 

• Use AES Encryption: Switch to AES encryption for Kerberos tickets. This will make them stronger and more secure. 
• Reduce Kerberos Ticket Lifetime: Shorten ticket lifetimes to minimize their usefulness if stolen. 

Deploy Network Segmentation & Firewall Rules 

Segmenting your network helps contain potential threats. 

• Isolate Domain Controllers with VLANs: Keep domain controllers apart from the main network. 
• Use Zero Trust Network Access (ZTNA): Block all unauthorized connections with a Zero Trust strategy. 

Enhancing Security Monitoring & Incident Detection 

The hardest part of securing AD is staying vigilant. Implementing advanced monitoring and detection measures ensures rapid response to threats. 

Enable Advanced Auditing & Log Analysis 

Proactively auditing sensitive actions strengthens your detection capabilities. 

• Monitor Critical Events: Keep an eye on Event IDs such as 4672 for privileged logins and 4728 for changes to Domain Admins. 
• Centralize Logging: Use Windows Event Forwarding (WEF) to consolidate logs for analysis. 

Deploy SIEM & Endpoint Detection Tools 

Leverage advanced tools to spot anomalies before they become incidents. 

• Integrate AD Logs with SIEM: Use SIEM tools like Splunk or Azure Sentinel. They help you get useful insights. 
• Use EDR for Endpoint Monitoring: EDR tools help find suspicious activity on devices. 

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