Networking basics, Preventing SQL Injection Attacks

SQL injection (SQLi) is a dangerous vulnerability that allows attackers to manipulate database queries through user input. This can lead to unauthorized access, data leakage, or even full system compromise. In this guide, you’ll learn how to prevent SQL injection in your applications.

What is SQL Injection?

SQL injection happens when user input is inserted directly into SQL queries without validation or escaping, allowing attackers to run arbitrary commands.

-- Dangerous example:
    SELECT * FROM users WHERE username = 'admin' AND password = '1234';

An attacker could inject input like:

' OR '1'='1

Turning the query into:

SELECT * FROM users WHERE username = '' OR '1'='1';

Step 1: Use Parameterized Queries

This is the single most effective way to prevent SQLi.

// Safe pseudocode
    stmt = db.prepare("SELECT * FROM users WHERE username = ? AND password = ?");
    stmt.bind(username, password);
    stmt.execute();

Step 2: Use ORM Libraries

Frameworks like SQLAlchemy, Sequelize, or Django ORM abstract away raw SQL and apply automatic protection.

Step 3: Validate and Sanitize Input

Ensure input matches expected formats (e.g., email, integers).
Reject or escape dangerous characters if raw SQL must be used.

Step 4: Use Least Privilege Access

Your application should connect to the database using a user with the minimum necessary privileges (e.g., read-only for reading data).

Step 5: Monitor and Log Database Activity

Track and analyze unusual query patterns to detect potential injection attempts.

Step 6: Employ Web Application Firewalls (WAFs)

A WAF can help detect and block common SQL injection payloads before they reach your server.

Next Steps

Test your application with tools like OWASP ZAP or sqlmap. Harden your database access code and always treat input as untrusted.