Web Application Security Basics

Web applications are prime targets for attackers. Understanding common vulnerabilities is crucial for both developers and security testers.

Common Web Vulnerabilities

1. SQL Injection

SQL injection occurs when user input is improperly sanitized, allowing attackers to manipulate database queries.

Example vulnerable code:

$query = "SELECT * FROM users WHERE username='$username'";

Prevention:

  • Use prepared statements
  • Implement input validation
  • Apply least privilege principle

2. Cross-Site Scripting (XSS)

XSS allows attackers to inject malicious scripts into web pages viewed by other users.

Types:

  • Reflected XSS
  • Stored XSS
  • DOM-based XSS

Prevention:

  • Sanitize user input
  • Encode output
  • Implement Content Security Policy (CSP)

3. Cross-Site Request Forgery (CSRF)

CSRF tricks users into performing unwanted actions on authenticated sessions.

Prevention:

  • Use CSRF tokens
  • Implement SameSite cookies
  • Verify origin headers

Testing Methodology

  1. Reconnaissance - Map the application
  2. Scanning - Identify potential vulnerabilities
  3. Exploitation - Attempt to exploit findings
  4. Reporting - Document all findings
  • Burp Suite - Comprehensive web testing platform
  • OWASP ZAP - Free alternative to Burp
  • SQLMap - Automated SQL injection tool
  • Nikto - Web server scanner

Best Practices

  • Always get written authorization
  • Test in controlled environments
  • Follow responsible disclosure
  • Keep detailed notes

Remember: The goal is to improve security, not cause harm!