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Secure your SQL Server

SQL Server is a relational database management system (RDBMS) that stores and manages critical business data for applications, analytics, and reporting. Because it often contains sensitive information, such as customer records, financial data, and intellectual property, securing SQL Server is essential to protect your organization from data breaches, unauthorized access, and compliance risks.

This article provides guidance on how to best secure your SQL Server.

Network security

Securing network access to SQL Server helps prevent unauthorized connections, reduces exposure to attacks, and ensures only trusted sources can reach your databases.

Identity management

Strong identity and authentication controls help ensure only authorized users and applications can access SQL Server resources.

  • Use Windows authentication or Microsoft Entra authentication: Prefer Windows authentication or Microsoft Entra authentication over SQL authentication for centralized identity management and easier account lifecycle control. For more information, see Choose an authentication mode.

  • Use group-managed service accounts (gMSA) for services: Use gMSA to manage service account credentials automatically and securely. For more information, see Group-Managed Service Accounts overview.

  • Enforce strong password policies: If you're using SQL authentication, require complex passwords that can't be easily guessed and aren't used for other accounts. Regularly update passwords and enforce Active Directory policies. For more information, see Strong passwords.

  • Use contained database users when appropriate: Consider contained database users for applications that need database-level authentication without requiring server-level logins. For more information, see Contained database users.

Privileged access

Limiting and monitoring privileged access helps prevent unauthorized changes and reduces the impact of compromised accounts.

  • Grant the minimum permissions required: Assign the lowest level of privilege needed for each user or service. Regularly review and adjust permissions to maintain least privilege. For more information, see Getting started with database engine permissions.

  • Separate database administrators (DBA) and sysadmin roles: Avoid granting sysadmin rights to all DBAs. Use the CONTROL SERVER permission when possible, as it respects DENY permissions and allows for more granular control. Consider a separation of duties that limit access to the virtual machine, the ability to log into the operating system, the ability to modify error and auditing logs, and the ability to install applications and/or features. For more information, see Permissions (Database Engine).

  • Monitor and audit privileged activities: Enable auditing to track changes made by privileged accounts and review logs regularly for suspicious activity. For more information, see SQL Server Audit (Database Engine).

  • Implement role separation: Place Active Directory users in AD groups, map AD groups to SQL Server roles, and grant SQL Server roles the minimum permissions required by applications. For more information, see Getting started with database engine permissions.

Data protection

Protecting data at rest and in transit is critical to prevent unauthorized disclosure or tampering.

  • Encrypt sensitive information with Always Encrypted: Use Always Encrypted and Always Encrypted with secure enclaves to protect sensitive data in SQL Server. Prefer randomized encryption for stronger security. For more information, see Always Encrypted.

  • Use Transparent Data Encryption (TDE) for database files: Enable TDE to encrypt database, backup, and tempdb files, protecting data if physical media is compromised. For more information, see Transparent Data Encryption (TDE).

  • Mask sensitive data with Dynamic Data Masking (DDM): Use DDM to obfuscate sensitive data in query results when encryption isn't possible. For more information, see Dynamic Data Masking.

  • Grant column-level permissions: Limit access to sensitive columns by granting SELECT, REFERENCES, or UPDATE permissions only to authorized users. For more information, see GRANT permissions.

  • Use Row-Level Security (RLS) to restrict data access: Implement RLS to ensure users only see data relevant to them. Use SESSION_CONTEXT for middle-tier applications where users share SQL accounts. For more information, see Row-Level Security.

  • Combine security features for maximum protection: Use Row-Level Security together with Always Encrypted or Dynamic Data Masking to maximize your organization's security posture. For more information, see Row-Level Security best practices.

Logging and threat detection

Comprehensive logging and monitoring help detect threats, investigate incidents, and meet compliance requirements.

  • Enable and configure SQL Server Audit: Audit access and changes to sensitive data and configurations at both the server and database level. Consider auditing tables and columns with sensitive data that have security measures applied to them. Regularly review audit logs, especially for tables containing sensitive information where complete security measures aren't possible. For more information, see SQL Server Audit (Database Engine).

  • Use ledger in SQL Server: Enable ledger to create an immutable record of changes to sensitive data, providing tamper-evident logging. For more information, see Configure a ledger database.

Backup and recovery

Reliable backup and recovery processes protect your data from loss due to failures, disasters, or attacks.

Security assessment and threat mitigation

Regularly assessing your SQL Server environment helps identify vulnerabilities and improve your security posture.

  • Limit enabled features to reduce attack surface: Enable only the SQL Server features required for your environment. For more information, see Surface area configuration.

  • Run vulnerability assessments: Use SQL Vulnerability Assessment in SSMS to discover and remediate potential database vulnerabilities. For more information, see SQL Vulnerability Assessment.

  • Classify and label sensitive data: Use SQL Data Discovery and Classification to identify and label sensitive data for better protection and compliance. For more information, see SQL Data Discovery and Classification.

  • Review and mitigate common threats: Protect against SQL injection, side-channel attacks, brute force, password spray, and ransomware by following recommended practices for input validation, patching, and access control. For more information, see SQL injection and Ransomware attacks.

  • Implement defense-in-depth security: Use multiple security capabilities targeted at different security scopes to provide comprehensive protection against various threats. For more information, see SQL Server security best practices.

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