SQL Injection Prevention – Protecting Your Database from Attacks

Overview

SQL Injection is one of the most common and dangerous security vulnerabilities in web applications. It occurs when attackers insert malicious SQL code into user input fields, potentially gaining unauthorized access to or manipulating your database.

Preventing SQL injection is essential for protecting sensitive data and maintaining application integrity.




What Is SQL Injection?

SQL injection happens when user input is directly included in SQL queries without proper validation or sanitization. This allows attackers to:

  • Bypass login forms
  • Read or modify confidential data
  • Execute administrative operations
  • Delete tables or entire databases


Example of Vulnerable Code (PHP + MySQL):


$username = $_POST['username'];
$password = $_POST['password'];
$query = "SELECT * FROM users WHERE username = '$username' AND password = '$password'";

If the attacker inputs: ' OR '1'='1
The query becomes: SELECT * FROM users WHERE username = '' OR '1'='1' AND password = ''
This always returns true, logging in without valid credentials.



How to Prevent SQL Injection


1. Use Prepared Statements (Parameterized Queries)

Prepared statements ensure that user inputs are treated as data, not code.


PHP + PDO Example:


$stmt = $pdo->prepare("SELECT * FROM users WHERE username = ? AND password = ?");
$stmt->execute([$username, $password]);

Python + SQLite Example:


cursor.execute("SELECT * FROM users WHERE username = ? AND password = ?", (username, password))


2. Use Stored Procedures (Carefully)

Stored procedures can help isolate SQL logic, but they must not concatenate raw input.


CREATE PROCEDURE GetUser(IN username VARCHAR(50))
BEGIN
   SELECT * FROM users WHERE username = username;
END;


3. Validate and Sanitize User Input

  • Allow only expected formats and characters
  • Use whitelisting (e.g., email regex, numeric ranges)
  • Avoid using unsanitized input in dynamic queries


4. Limit Database Permissions

  • Do not connect to the database as a superuser
  • Create restricted users with only required permissions
  • Disable dangerous operations for app users (e.g., DROP, DELETE)


5. Use ORM (Object-Relational Mapping) Libraries

Frameworks like Django, Laravel, Hibernate, etc., abstract SQL operations and automatically escape input.



Bonus Measures

  • Use Web Application Firewalls (WAFs)
  • Monitor logs for suspicious queries
  • Employ input encoding in front-end forms
  • Implement rate-limiting to stop automated attacks


Common Myths

  • "Stored procedures always prevent injection" - Only if written securely
  • "Input sanitization is enough" - Must be combined with prepared statements
  • "Injection only affects login forms" - It can target any SQL query


Conclusion

SQL injection remains a critical threat to web applications, but it's entirely preventable with proper coding practices. Always use parameterized queries, validate all user input, and follow the principle of least privilege for database access. By implementing these security measures, you can protect your application from one of the most common cyber attacks.