Legacy vs. Cloud: Bridging the Security Gap Between AD and Microsoft Entra ID

Core Architecture: Traditional vs. Cloud-Native

Active Directory (AD), the backbone of enterprise identity for over two decades, is an on-premises directory service that uses Kerberos and NTLM for authentication. It operates within a domain-trust model, built for internal networks.

Microsoft Entra ID, formerly Azure AD, is a cloud-native identity and access management (IAM) solution engineered for today’s distributed workforce. It supports federation and authentication for thousands of cloud applications using modern protocols like OAuth 2.0, OpenID Connect, and SAML. Entra ID powers Microsoft 365, Azure services, and various SaaS platforms.

Authentication: Static Credentials vs. Adaptive Identity

AD relies on password-based authentication with Kerberos ticketing. While effective within controlled environments, this model is increasingly vulnerable to credential theft and lateral movement attacks.

Microsoft Entra ID uses token-based authentication (JWTs) and supports robust, adaptive access controls such as:

Multi-Factor Authentication (MFA)
Passwordless authentication
Conditional Access policies
Risk-based sign-in evaluation

These features position Entra ID as a strong choice for securing remote access, mobile workforce, and cloud-first environments.

Attack Techniques: Where and How Threats Evolve

Both Active Directory and Microsoft Entra ID are high-value targets, but their differing architectures mean attackers use different techniques to exploit them:

Threat Area	Active Directory (AD)	Microsoft Entra ID
Credential Theft	Pass-the-Hash, Golden Ticket, Mimikatz	Token theft, Consent phishing, Token replay
Lateral Movement	RDP, SMB, PsExec, WMI	OAuth abuse, Token misuse, Privilege escalation via roles
Persistence	AdminSDHolder, Service Accounts, GPO abuse	App registration abuse, MFA fatigue attacks

Security teams must customize their defenses to address the unique vulnerabilities of each platform.

Visibility and Logging: Monitoring Identity Footprints

In AD environments, visibility is achieved through Windows Event Logs (e.g., Event IDs 4624, 4768, 4672), combined with telemetry from tools like Sysmon and third-party log management platforms.

Microsoft Entra ID provides comprehensive cloud-native telemetry, including:

Sign-in logs – Track successful and failed login attempts
Audit logs – Record changes to user/group/role configurations
Risk detections – Identify suspicious sign-in behavior using machine learning

To strengthen threat correlation and incident response, hybrid environments should consolidate identity telemetry into a SIEM like Microsoft Sentinel.

Defense in Depth: Hardening Both Worlds

Best practices for securing Active Directory (AD):

Enforce Tiered Administration Models to isolate privileges
Deploy LAPS (Local Administrator Password Solution) for local credential management
Regularly audit privileged group memberships
Apply hardened Group Policy Objects (GPOs) to enforce security baselines

Best security practices for Microsoft Entra ID:

Enforce MFA and implement Conditional Access policies tailored to risk
Use Privileged Identity Management (PIM) for just-in-time access
Review enterprise app consents and API permissions
Enable Microsoft Entra Identity Protection to detect and mitigate risky sign-ins

In-depth defense is essential when securing hybrid identity ecosystems.

Tooling and Integration: Building a Unified View

Both AD and Entra ID can integrate into SIEM platforms, but the integration approach varies:

AD log forwarding often depends on agents, scripts, or third-party solutions.
Entra ID supports API-based log streaming and integrates natively with:
- Microsoft Defender for Identity
- Defender for Cloud Apps
- Microsoft Entra Identity Protection

This unified telemetry allows for automated, real-time threat detection and response across both identity platforms.

Security Verdict: Which One Is More Secure?

There’s no one-size-fits-all answer; it depends on how each environment is configured and maintained.

A well-hardened AD can be secure but demands continuous patching and monitoring.
Microsoft Entra ID offers built-in defenses, but misconfigurations (e.g., excessive app permissions or weak Conditional Access rules) can introduce risk.

In hybrid identity models, attackers often move laterally between both platforms, making it critical to secure them together.

The Hybrid Identity Bridge: A Critical Risk Surface

Most organizations connect AD and Entra ID via Azure AD Connect or Entra Connect. If not properly secured, this synchronization bridge can become a high-risk target.

Common risks include:

Weak protection of sync accounts
Exploitation of password hash synchronization
Overprivileged cloud roles tied to on-prem accounts

Mitigation strategies:

Apply least privilege to sync and admin accounts
Monitor synchronization logs and anomalies
Use Conditional Access for sensitive operations
Audit role assignments and password policies regularly

The hybrid bridge must be treated as a high-value asset in your identity architecture.

Final Thoughts

Microsoft Entra ID and Active Directory are not competitors; they’re complementary elements of a modern identity stack. As organizations evolve into hybrid and multi-cloud ecosystems, security models must adapt by: