Securing SQL Server on Azure: Best Practices for PaaS, IaaS, and SaaS Deployments

Introduction

Security comes first when working in big projects for Government or Enterprises. Sometimes the whole project may be suspended or revalidated not for technical reasons -there are a lot - but to ensure platform security from the network/app entry point to where data resides on disk.

SQL Server security in Azure requires different approaches depending on your deployment model: PaaS (Azure SQL Database/Managed Instance), IaaS (SQL Server on Azure VMs), or SaaS-integrated databases. This guide covers security best practices for each scenario.

1. Securing Azure SQL Database (PaaS)

Azure SQL Database is a fully managed PaaS service with built-in security, but additional hardening is required.

A. Authentication & Access Control

• Use Azure AD Authentication (instead of SQL logins)
• Implement Row-Level Security (RLS) for data filtering
• Enable Multi-Factor Authentication (MFA) for admin accounts

B. Network Security

• Disable Public Network Access (use Private Endpoints)
• Configure NSGs to restrict access to trusted IPs
• Enable Azure Private Link for secure PaaS connectivity

C. Encryption & Data Protection

• Transparent Data Encryption (TDE) (AES-256) enabled by default
• Always Encrypted for sensitive columns (e.g., PII, financial data)
• Azure Key Vault Integration for managing encryption keys

D. Monitoring & Threat Detection

• Enable Microsoft Defender for SQL (formerly ATP)
• Audit Logging (send logs to Azure Monitor or Log Analytics)
• Set Up Alerts for suspicious activities (e.g., SQL injection attempts)

2. Securing SQL Server on Azure VMs (IaaS)

When running SQL Server on Azure VMs, you manage the OS and SQL instance.

A. VM & Network Hardening

• Place SQL VM in a Dedicated Subnet (isolate from web apps)
• Use Azure Firewall/NSGs to block unnecessary ports (allow only 1433, 1434)
• Enable Just-In-Time (JIT) VM Access to reduce attack surface

B. SQL Server Configuration

• Disable SA Account (or rename it)
• Use Windows Authentication (preferred over SQL auth)
• Enable TDE (if not using Azure SQL PaaS)
• Patch SQL Server Regularly (Azure Update Management)

C. Backup & Disaster Recovery

✅ Automated Backups (Azure Backup for SQL VMs) ✅ Geo-Replication (for critical workloads) ✅ Test Restores to ensure recovery readiness

3. Securing SQL in SaaS Applications

If your SaaS solution (e.g., Custom App, Dynamics 365) uses SQL, follow these steps:

A. SaaS Provider Responsibilities

✔ Ensure encryption (TDE, TLS 1.2+) ✔ Verify compliance (SOC 2, ISO 27001, NCA, GDPR) ✔ Request audit logs (if available)

B. Customer Responsibilities

• Use Strong Passwords & RBAC (least privilege access)
• Enable Logging (if SaaS allows exporting logs)
• Monitor for Data Leaks (Microsoft Purview/DLP)

4. Universal Best Practices (All Deployment Models)

A. Data Masking & Anonymization

• Dynamic Data Masking (DDM) (hide sensitive data from non-admins)
• Static Data Masking (for dev/test environments)

B. SQL Injection Prevention

• Use Parameterized Queries (avoid dynamic SQL)
• Deploy WAF (Azure Front Door/Application Gateway)

C. Compliance & Auditing

• Enable SQL Auditing (track logins, schema changes)
• Retain Logs for 12+ Months (for NCA/GDPR compliance)

5. Recommended Tools for SQL Security

• Microsoft Defender for SQLThreat detectionPaaS, IaaS
• Azure Key VaultKey managementPaaS, IaaS
• Azure Private LinkSecure PaaS access, PaaS
• Azure PolicyEnforce security rules,PaaS, IaaS
• Azure PurviewData governance,SaaS, PaaS

Conclusion

• For PaaS (Azure SQL Database): Leverage built-in security (TDE, Azure AD, Defender for SQL).
• For IaaS (SQL on VMs): Harden the OS, enable JIT access, and patch regularly.
• For SaaS: Verify provider compliance and enforce RBAC.