SQL Server Database Engine Security
This document provides a comprehensive guide to securing your SQL Server Database Engine. Security is paramount in protecting your valuable data from unauthorized access, modification, or deletion. This section covers various aspects of SQL Server security, from authentication and authorization to data encryption and auditing.
Authentication and Authorization
Understanding and implementing robust authentication and authorization mechanisms is the first step in securing your SQL Server instance.
Authentication
SQL Server supports two primary authentication modes:
- Windows Authentication: Leverages the security provided by Windows. User accounts are managed by Active Directory or local Windows accounts. This is generally the recommended and more secure method.
- SQL Server Authentication: Uses user IDs and passwords created and managed directly within SQL Server. This mode requires careful management of strong passwords and is less secure if not properly configured.
You can configure the authentication mode during installation or modify it later through SQL Server Management Studio (SSMS).
Authorization
Once authenticated, users are granted specific permissions to access and manipulate data. This is handled through:
- Logins: Represents an account that can connect to the SQL Server instance.
- Users: Represents an account within a specific database. A login is mapped to a user.
- Roles: Collections of permissions that can be assigned to users, simplifying permission management. Server-level roles and database-level roles exist.
- Permissions: Specific actions that can be performed on securable objects (e.g., SELECT, INSERT, UPDATE, DELETE on a table, EXECUTE on a stored procedure).
Securing Data
Beyond controlling access, SQL Server offers features to protect the data itself.
Encryption
Encryption helps protect sensitive data both at rest (stored in database files) and in transit (moving across the network).
- Transparent Data Encryption (TDE): Encrypts the entire database, including data files and log files. This protects data from being read if the underlying storage is compromised.
- Column-Level Encryption: Encrypts specific sensitive columns within a table.
- Always Encrypted: A client-side encryption technology that ensures sensitive data is never exposed in plain text on the server.
- SSL/TLS Encryption: Encrypts data in transit between the client and the server.
Data Masking
Dynamic Data Masking limits sensitive data exposure by transforming it to non-sensitive data to non-privileged users. This can be applied to specific columns.
Auditing and Monitoring
Regular auditing and monitoring are crucial for detecting security breaches and ensuring compliance.
SQL Server Audit
SQL Server Audit allows you to create server audits and database audits to track database events. You can specify which actions to audit, such as logins, failed logins, or DDL changes.
Extended Events
Extended Events is a flexible and scalable system for monitoring and troubleshooting SQL Server. It can be used to capture detailed information about various server activities, including security-related events.
Log Management
Regularly review SQL Server error logs, Windows Event Logs, and audit logs for suspicious activities.
Common Security Threats and Mitigations
Be aware of common threats and how to defend against them:
- SQL Injection: A technique where malicious SQL statements are inserted into input fields. Mitigate by using parameterized queries or stored procedures and validating user input.
- Brute-Force Attacks: Attempting to guess passwords by trying many combinations. Mitigate by enforcing strong password policies, using account lockout, and enabling Windows Authentication.
- Privilege Escalation: Malicious actors attempting to gain higher privileges than they are authorized for. Mitigate by strictly managing database roles and permissions, and monitoring for unusual activity.