What is a Web Application Firewall?
A Web Application Firewall (WAF) is a security solution that monitors, filters, and blocks HTTP/HTTPS traffic to and from web applications. It protects against common web exploits like SQL injection, cross-site scripting (XSS), and other OWASP Top 10 vulnerabilities.
How WAFs Work
Request Inspection
- Examine HTTP headers
- Analyze request body
- Check query parameters
Pattern Matching
- Signature-based detection
- Regular expression rules
- Known attack patterns
Behavioral Analysis
- Anomaly detection
- Rate limiting
- Bot detection
Deployment Models
Network-Based
- Hardware appliance
- Low latency
- Higher cost
Host-Based
- Software on server
- Application-specific
- More configuration
Cloud-Based
- SaaS delivery
- Easy deployment
- Scalable
Protection Capabilities
OWASP Top 10
- SQL injection
- XSS
- CSRF
- Broken authentication
Custom Rules
- Application-specific
- Business logic protection
Bot Management
- Good vs. bad bots
- Scraping prevention
- Credential stuffing defense
Popular WAF Solutions
Cloud
- AWS WAF
- Cloudflare
- Akamai
- Azure WAF
Self-Hosted
- ModSecurity
- NGINX App Protect
- F5 Advanced WAF
Best Practices
- Start in detection mode
- Tune rules for your application
- Monitor false positives
- Regular rule updates
- Combine with other controls
- Log and analyze traffic