Web Application Firewall (WAF)

A WAF sits between users and web applications, inspecting requests and blocking malicious traffic. Unlike network firewalls, WAFs understand web application protocols and detect application-layer attacks.

Attacks WAFs protect against:

• SQL injection: Malicious SQL through input fields
• Cross-site scripting (XSS): Injecting malicious scripts
• Cross-site request forgery (CSRF): Tricking users into unintended actions
• DDoS: Overwhelming applications with traffic
• Bot attacks: Credential stuffing, scraping, spam
• File inclusion: Including malicious remote files
• Directory traversal: Accessing files outside web root

WAF deployment models:

• Cloud-based (CDN-integrated): Cloudflare, AWS WAF, Azure Front Door
• Cloud-based (standalone): Imperva, Sucuri
• Built into cloud platforms: AWS WAF, Azure WAF, GCP Cloud Armor

Configuration approaches:

• Managed rule sets: Pre-built OWASP Top 10 protection
• Custom rules: Application-specific protections
• Rate limiting: Controlling request volume per IP
• Geoblocking: Blocking specific country traffic
• Bot management: Distinguishing legitimate from malicious bots

Best practices:

• Start in detection mode to avoid false positives
• Gradually enable blocking as rules are tuned
• Review blocked requests for patterns
• Use managed rules as baseline, add custom rules
• Integrate WAF logging with security monitoring