What is SQL Injection?

SQL Injection is a security vulnerability that allows an attacker to interfere with the queries an application makes to its database. It happens when user inputs are not properly sanitized and are directly included in SQL statements, letting attackers manipulate the query to access, modify, or delete data unauthorizedly.

How SQL Injection Works

Suppose you have this unsafe query in your code:

SELECT * FROM users WHERE username = ' " + userInput + " ';

If userInput is:

' OR '1'='1

The query becomes:

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

Since '1'='1' is always true, this returns all users, potentially bypassing authentication.

Common Types of SQL Injection Attacks

• Authentication bypass

• Data theft or exposure

• Data modification or deletion

• Executing administrative operations on the database

How to Prevent SQL Injection

1. Use Prepared Statements (Parameterized Queries):

Example in many languages (e.g., PHP, Python, Java):

SELECT * FROM users WHERE username = ? AND password = ?;

User input is sent separately, so it cannot change query structure.

2. Use Stored Procedures:

Stored procedures also help isolate user input from SQL logic.

3. Validate and Sanitize User Input:

Make sure inputs conform to expected formats (e.g., no special characters).

4. Use ORM Libraries:

Most Object-Relational Mappers handle parameterization automatically.

5. Least Privilege Principle:

Database users should have minimum required permissions.

Summary

• SQL Injection is a critical security risk.

• Always use parameterized queries or prepared statements.

• Never directly concatenate user inputs into SQL queries.

If you want, I can help you write safe SQL queries or review code to avoid SQL Injection!