SQL Injection(SQLi)

What is SQL Injection?
SQL Injection (SQLi) is a web security vulnerability where attackers inject malicious SQL code into application input fields to manipulate backend databases.

Common target areas:

• Login forms
• Search bars
• URL parameters
• Registration forms

Why SQL Injection Happens

SQLi occurs when applications:

• Trust user input directly
• Use insecure dynamic SQL queries
• Fail to validate or sanitize input properly

Risks of SQL Injection

Attackers can:

• Bypass authentication
• Steal sensitive information
• Modify or delete records
• Access administrator accounts
• Compromise entire databases

Types of SQL Injection

In-Band SQLi

Attackers receive direct responses from the application.

• Error-Based SQLi
• UNION-Based SQLi
   

Blind SQLi

Attackers identify vulnerabilities through application behavior.

• Boolean-Based SQLi
• Time-Based SQLi
   

Out-of-Band SQLi

Attackers extract data using external channels such as DNS or HTTP requests.

Common SQL Injection Techniques

OR 1=1 Attack

' OR 1=1 --

Purpose : Bypass login authentication

Comment Injection

--
/* */

Purpose : Ignore remaining SQL query parts

Batch Query Injection

'; DROP TABLE users; --

Purpose : Execute multiple SQL commands

UNION-Based Injection

UNION SELECT username, password FROM users;

Purpose : Extract sensitive database data

Impact of SQL Injection

SQL Injection attacks may cause:

• Financial losses
• Data breaches
• Reputation damage
• Legal penalties
• System compromise

SQL Injection Prevention

Use Parameterized Queries
client.query(
 'SELECT * FROM users WHERE id=$1',
 [userId]
);

Validate User Input

• Restrict invalid characters
• Apply type checking
• Use input filtering

Apply Least Privilege Principle
Database accounts should only have necessary permissions.

Use Web Application Firewall (WAF)
WAF helps detect and block malicious SQL requests.

SQL Injection Testing Tools

sqlmap : Automated SQL Injection testing tool

Burp Suite :  Web application security testing platform

OWASP ZAP :  Open-source vulnerability scanner

Conclusion
SQL Injection is one of the most critical web application vulnerabilities. It allows attackers to manipulate databases and access sensitive information.

Best Security Practices

• Use parameterized queries
• Validate all user inputs
• Avoid dynamic SQL queries
• Perform regular security testing
• Apply least privilege access controls