Build a Web Application Firewall (WAF) for Small Websites

Many small websites don’t have the budget or resources for enterprise-grade security tools, leaving them vulnerable to common attacks. A custom, lightweight WAF can provide essential protection by filtering malicious inputs and detecting suspicious behavior in real time.

The goal is to develop a middleware or proxy-layer WAF that inspects incoming requests, applies rules to detect attack patterns, and blocks or logs threats. It can be integrated into existing Flask, Node.js, or PHP sites with minimal effort.

Incoming requests are intercepted by the WAF layer before reaching the app backend. It checks the request method, headers, body, and query parameters against a set of rules or signatures. If a threat is detected, the request is blocked, logged, or redirected to an error page.

• Analyze incoming GET/POST requests for known attack payloads.
• Sanitize inputs or reject them if they match SQLi/XSS patterns.
• Track request frequency per IP and apply rate-limiting policies.
• Allow admin customization of blocklists or rule sets.
• Generate reports on detected threats for auditing purposes.

• OWASP Top 10 Web Vulnerabilities
• ModSecurity WAF Rules
• Express Middleware Docs
• Flask Middleware Guide
• Regex Patterns for Attack Detection