Web Application Firewall (WAF): How It Protects You
A Web Application Firewall (WAF) inspects HTTP/HTTPS traffic between users and your web application, filtering and blocking malicious requests before they reach your application. It is a critical defence layer for public-facing web applications.
What a WAF Protects Against
- SQL injection attacks
- Cross-site scripting (XSS) attempts
- CSRF attacks
- Path traversal attacks
- Bot traffic and automated scanning
- DDoS at the application layer (Layer 7)
- Malformed HTTP requests
- Known vulnerability exploit patterns (CVE-based rules)
How WAFs Work
WAFs inspect request content against rule sets. Rules can be: signature-based (matching known attack patterns), rate-based (blocking sources that exceed request thresholds), and behavioural (detecting anomalies from normal traffic patterns). Modern WAFs also use machine learning to adapt to new attack patterns.
WAF Options We Use
- Cloudflare WAF: Suitable for most applications — low setup friction, managed rule sets, excellent DDoS protection
- AWS WAF: Deep integration with AWS services. Highly configurable with managed rule groups.
- Azure Front Door WAF: For Azure-hosted applications, integrated with Azure's CDN and routing
Limitations
A WAF is a defence layer, not a replacement for secure application code. Business logic vulnerabilities and application-specific flaws require application-level security — a WAF cannot protect against vulnerabilities it does not know about.