CAPTCHA-based Brute Force Attack Prevention - Technical & Engineering Guide
1. Introduction
1.1 Purpose
This guide provides a comprehensive overview of implementing CAPTCHA as a method to prevent brute force attacks on web applications. CAPTCHAs are widely used to distinguish between human users and automated bots, making it difficult for attackers to automate login attempts.
1.2 Scope
This project demonstrates how to integrate CAPTCHA into web applications for login, registration, or other sensitive operations. It targets developers, cybersecurity professionals, and students interested in enhancing application security.
1.3 Definitions & Acronyms
|
Acronym |
Definition |
|
CAPTCHA |
Completely Automated Public Turing test to tell Computers and Humans Apart. |
|
Brute Force Attack |
A trial-and-error method used to decode sensitive data such as passwords. |
|
API |
Application Programming Interface - allows communication between software applications. |
2. System Architecture
The CAPTCHA-based brute force prevention system includes:
- **CAPTCHA Generation Module**: Dynamically generates CAPTCHAs.
- **User Verification Module**: Validates user responses.
- **Integration Layer**: Embeds CAPTCHA into web forms.
- **Logging and Analytics**: Tracks failed attempts and CAPTCHA activity.
3. Key Features
3.1 Dynamic CAPTCHA Generation
Generates CAPTCHAs using text, images, or audio to ensure variety and challenge for bots.
3.2 Adaptive Complexity
Increases CAPTCHA difficulty based on the number of failed attempts.
3.3 Seamless Integration
Easily integrates with web application login pages, registration forms, or other input-sensitive areas.
4. Implementation Steps
1. **Environment Setup**: Install necessary frameworks like
Django, Flask, or Node.js for your web application.
2. **CAPTCHA Library**: Use libraries like reCAPTCHA (Google) or custom
implementations.
3. **Backend Integration**: Embed CAPTCHA validation in the backend logic of
login and registration forms.
4. **Dynamic Adjustment**: Implement logic to adjust CAPTCHA complexity
dynamically.
5. **Logging and Monitoring**: Track login attempts and log unusual activities.
6. **Testing**: Test with various scenarios, including normal user behavior and
simulated brute force attacks.
5. Security Considerations
1. Ensure CAPTCHAs are user-friendly and accessible (e.g.,
provide audio alternatives).
2. Avoid predictable CAPTCHA patterns.
3. Monitor logs for signs of CAPTCHA bypass techniques.
6. Tools and Technologies
- **CAPTCHA Providers**: Google reCAPTCHA, hCaptcha
- **Programming Languages**: Python, JavaScript
- **Web Frameworks**: Django, Flask, Express.js
- **Testing Tools**: OWASP ZAP, Burp Suite
7. Testing and Validation
1. Test with different browsers and devices for
compatibility.
2. Simulate brute force attacks to validate CAPTCHA effectiveness.
3. Verify accessibility for all users, including those with disabilities.