SQL Server Auditing & Compliance: How to Track Data Access

Introduction

In today's data-driven world, tracking who accesses what information in your SQL Server databases is critical for both security and compliance. Whether you're subject to regulations like GDPR, HIPAA, SOX, or simply maintaining internal security policies, implementing proper auditing in SQL Server is essential.

This guide will walk you through the various methods available for tracking data access in SQL Server, from native auditing features to custom solutions.

Why Audit SQL Server Data Access?

Before diving into the "how," let's examine the "why":

1. Compliance requirements: Many regulations mandate tracking of sensitive data access

2. Security monitoring: Detect unauthorized access attempts or suspicious patterns

3. Forensic analysis: Investigate data breaches or leaks after they occur

4. Accountability: Know exactly who accessed or modified critical data

Native SQL Server Auditing Features

1. SQL Server Audit

SQL Server's built-in auditing capability (available in Enterprise, Developer, and Evaluation editions) provides a comprehensive framework:

-- Create a server audit
USE master;
GO
CREATE SERVER AUDIT MyServerAudit
    TO FILE (FILEPATH = 'C:\Audits\')
    WITH (QUEUE_DELAY = 1000, ON_FAILURE = CONTINUE);
GO
ALTER SERVER AUDIT MyServerAudit WITH (STATE = ON);
GO

-- Create a database audit specification
USE YourDatabase;
GO
CREATE DATABASE AUDIT SPECIFICATION MyDatabaseAudit
FOR SERVER AUDIT MyServerAudit
ADD (SELECT, INSERT, UPDATE, DELETE ON SCHEMA::dbo BY public);
GO
ALTER DATABASE AUDIT SPECIFICATION MyDatabaseAudit WITH (STATE = ON);
GO

2. Change Data Capture (CDC) and Change Tracking

For tracking data modifications:

-- Enable CDC at database level
USE YourDatabase;
GO
EXEC sys.sp_cdc_enable_db;
GO

-- Enable CDC for a specific table
EXEC sys.sp_cdc_enable_table
    @source_schema = 'dbo',
    @source_name = 'YourTable',
    @role_name = NULL;
GO

3. SQL Server Profiler and Extended Events

While not recommended for production auditing (due to performance impact), these tools can be useful for targeted monitoring:

-- Create an Extended Events session for login tracking
CREATE EVENT SESSION [LoginAudit] ON SERVER
ADD EVENT sqlserver.login(
    ACTION(sqlserver.client_hostname,sqlserver.username))
ADD TARGET package0.event_file(SET filename=N'C:\Audits\LoginAudit.xel')
WITH (MAX_MEMORY=4096 KB, MAX_DISPATCH_LATENCY=30 SECONDS);
GO

Custom Auditing Solutions

When native features don't meet all requirements, consider:

1. Audit Triggers

CREATE TRIGGER tr_AuditTableAccess
ON dbo.YourTable
AFTER SELECT, INSERT, UPDATE, DELETE
AS
BEGIN
    SET NOCOUNT ON;
    
    DECLARE @OperationType VARCHAR(10);
    DECLARE @UserName NVARCHAR(128) = SUSER_SNAME();
    DECLARE @HostName NVARCHAR(128) = HOST_NAME();
    
    IF EXISTS(SELECT * FROM inserted) AND EXISTS(SELECT * FROM deleted)
        SET @OperationType = 'UPDATE';
    ELSE IF EXISTS(SELECT * FROM inserted)
        SET @OperationType = 'INSERT';
    ELSE IF EXISTS(SELECT * FROM deleted)
        SET @OperationType = 'DELETE';
    ELSE
        SET @OperationType = 'SELECT';
    
    INSERT INTO dbo.AuditLog(TableName, OperationType, UserName, HostName, Timestamp)
    VALUES ('YourTable', @OperationType, @UserName, @HostName, GETDATE());
END;
GO

2. Temporal Tables

For tracking all data changes:

-- Create a temporal table
CREATE TABLE dbo.YourTable
(
    ID INT PRIMARY KEY,
    Data NVARCHAR(100),
    ValidFrom DATETIME2 GENERATED ALWAYS AS ROW START,
    ValidTo DATETIME2 GENERATED ALWAYS AS ROW END,
    PERIOD FOR SYSTEM_TIME (ValidFrom, ValidTo)
)
WITH (SYSTEM_VERSIONING = ON (HISTORY_TABLE = dbo.YourTable_History));

Best Practices for SQL Server Auditing

1. Define clear audit requirements based on compliance needs

2. Focus on sensitive data to avoid performance overhead

3. Secure audit logs - protect them from tampering

4. Regularly review logs - automated alerts for suspicious activity

5. Document your audit policy - what's being tracked and why

6. Test performance impact before deploying to production

7. Archive old logs - but keep them accessible when needed

Compliance Considerations

Different regulations have specific requirements:

• GDPR: Right to be forgotten, data access logs

• HIPAA: Access to protected health information

• SOX: Financial data modifications

• PCI DSS: Credit card data access

Ensure your audit solution meets the specific requirements for your industry.

Third-Party Audit Solutions

When native tools aren't sufficient, consider specialized solutions like:

1. ApexSQL Audit

2. SQL Compliance Manager

3. IBM Guardium

4. Imperva SecureSphere

These typically offer:

• Centralized audit collection

• Advanced reporting

• Real-time alerts

• Lower performance overhead

Conclusion

Implementing proper SQL Server auditing is a critical component of your data security and compliance strategy. By leveraging SQL Server's native features combined with custom solutions where needed, you can create a robust audit trail that meets regulatory requirements and helps protect your sensitive data.

Remember that auditing is not a "set it and forget it" solution. Regular review of audit logs and periodic reassessment of your audit policies are essential to maintaining an effective security posture.