Blog | G5 Cyber Security

Web Application Security: A Practical Guide

G5 Cyber Security

TL;DR

This guide helps you understand and improve the security of your web applications. We’ll cover common threats, how to prevent them, and tools to help you along the way.

1. Understand Common Web Application Threats

  1. SQL Injection: Attackers insert malicious SQL code into input fields to gain access to your database.
  2. Cross-Site Scripting (XSS): Attackers inject malicious scripts into websites viewed by other users.
  3. Cross-Site Request Forgery (CSRF): Attackers trick users into performing actions they didn’t intend to on a website where they are authenticated.
  4. Broken Authentication: Weak passwords, lack of multi-factor authentication, and session management issues.
  5. Security Misconfiguration: Default settings left unchanged, unnecessary features enabled, and unpatched software.
  6. Sensitive Data Exposure: Unprotected storage or transmission of sensitive information like passwords, credit card details, and personal data.

2. Preventing SQL Injection

  1. Use Parameterized Queries (Prepared Statements): This is the most effective defense. It separates the SQL code from the user input. 
    # Example in Python with a database library
cursor.execute("SELECT * FROM users WHERE username = %s", (username,))
  2. Input Validation: Sanitize and validate all user inputs to ensure they conform to expected formats.
  3. Least Privilege Principle: Grant database users only the necessary permissions.

3. Preventing Cross-Site Scripting (XSS)

  1. Output Encoding/Escaping: Encode user input before displaying it on your website. 
    # Example in PHP
echo htmlspecialchars($userInput, ENT_QUOTES, 'UTF-8');
  2. Content Security Policy (CSP): Define a whitelist of sources from which the browser is allowed to load resources.
  3. HTTPOnly Cookies: Prevent JavaScript access to cookies containing sensitive information. 
    # Example in HTTP header:
Set-Cookie: sessionid=...; HttpOnly

4. Preventing Cross-Site Request Forgery (CSRF)

  1. Use Anti-CSRF Tokens: Include a unique, unpredictable token in each form submission. 
    # Example in HTML:
<input type="hidden" name="csrf_token" value="{{ csrf_token }}"//>
  2. SameSite Cookies: Configure cookies to only be sent with requests originating from the same domain. 
    # Example in HTTP header:
Set-Cookie: sessionid=...; SameSite=Strict
  3. Check Referer Header (with caution): Verify that the request originated from your own website. This is less reliable than tokens.

5. Secure Authentication

  1. Strong Password Policies: Enforce minimum length, complexity requirements, and regular password changes.
  2. Multi-Factor Authentication (MFA): Require users to provide multiple forms of identification.
  3. Secure Session Management: Use strong session IDs, implement session timeouts, and regenerate session IDs after login. 
    # Example in PHP:
session_regenerate_id(true);
  4. Rate Limiting: Limit the number of failed login attempts to prevent brute-force attacks.

6. Security Misconfiguration Best Practices

  1. Keep Software Updated: Regularly patch your operating system, web server, and application frameworks.
  2. Remove Unnecessary Features: Disable or uninstall any features you don’t need.
  3. Configure Error Handling Properly: Avoid displaying sensitive information in error messages. 
    # Example - avoid showing stack traces to users!
  4. Use HTTPS: Encrypt all communication between the client and server using TLS/SSL certificates.

7. Tools for Web Application Security

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