Introduction

As cyber threats continue to evolve, securing your web applications is more critical than ever. Microsoft Azure provides a powerful native solution: Azure Web Application Firewall (WAF), which protects your apps from common web vulnerabilities and attacks such as SQL injection, Cross-site scripting (XSS), and more.

In this blog, we'll explore what Azure WAF is, its features, deployment modes, configuration strategies, and best practices to secure your applications efficiently.

🌐 What Is Azure WAF?

Azure Web Application Firewall is a cloud-native security service that protects web applications from malicious attacks by filtering, monitoring, and blocking harmful HTTP/S traffic.

It is deeply integrated with:

Azure Application Gateway
Azure Front Door
Azure CDN (Preview)

This flexibility allows you to choose the right deployment based on your performance, availability, and geographic needs.

🧱 Key Features of Azure WAF

Feature	Description
OWASP Ruleset	Protects against common vulnerabilities based on the Open Web Application Security Project (OWASP) Core Rule Sets (CRS)
Custom Rules	Create rules based on IPs, geolocation, request methods, query strings, headers, etc.
Bot Protection	Mitigates bot traffic and scrapers
Geo-Blocking	Blocks requests based on the region
Rate Limiting	Limits the number of requests to prevent DDoS-style abuse
Logging & Monitoring	Integrates with Azure Monitor, Log Analytics, and Microsoft Defender for Cloud

🏗️ Deployment Options

Azure WAF can be deployed with the following services:

1. Azure Application Gateway WAF

Best for: Regional, stateful, and internal applications
Features: Autoscaling, SSL termination, cookie-based session affinity
Modes: Detection / Prevention

2. Azure Front Door WAF

Best for: Global applications, CDN-enabled content, low latency delivery
Features: Layer 7 routing, global load balancing, automatic failover
Modes: Detection / Prevention

3. Azure CDN WAF (Preview)

Best for: High-volume static content protection
Note: Still in preview with limited rule sets

🛡️ Modes: Detection vs Prevention

Mode	Behavior
Detection	Logs all potentially malicious requests without blocking
Prevention	Actively blocks malicious requests in real time

🔎 Recommendation: Start with Detection mode to monitor traffic and validate rules before switching to Prevention mode.

⚙️ Creating and Configuring WAF Policies

To apply WAF protections, you need to create a WAF Policy, then associate it with your Azure resource (e.g., Application Gateway or Front Door).

WAF Policy Configuration Includes:

Managed Rules (OWASP): Enable/disable individual rules or rule sets
Custom Rules: Create specific match conditions
Exclusions: Skip rules for trusted request patterns
Rate Limit Rules: Prevent abuse from specific clients
Bot Protection (Preview)

💡 Tip: Use Log Analytics or Diagnostic settings to forward logs for auditing and troubleshooting.

🧪 Real-World Example Use Case

Scenario: A healthcare web portal must block SQL injection attempts while allowing trusted IPs from internal networks.

Solution:

Deploy Azure Application Gateway with WAF
Enable OWASP CRS 3.2
Add Custom Rule: Allow traffic from internal IP ranges
Add Custom Rule: Block requests with SQL keywords in the query string
Start in Detection mode, then move to Prevention after testing

✅ Best Practices for Azure WAF

Start with Detection Mode
Understand the impact of rules before enforcing them.
Customize Rules for Your App
Tailor WAF policies to your specific endpoints and parameters.
Enable Logging and Alerts
Integrate with Azure Monitor for visibility and response automation.
Regularly Update Rule Sets
Stay aligned with new OWASP versions and threats.
Use Rate Limiting
Protect against brute-force and scraping attacks.
Review Logs and Tuning
Fine-tune policies based on false positives and legitimate traffic.

📊 Monitoring WAF

Azure WAF provides detailed logging:

Blocked Requests
Rule Matches
Client IPs and URLs
Geographic Source of Traffic

Use tools like:

Azure Monitor
Log Analytics
Sentinel (for advanced threat detection)

🔚 Conclusion

Azure WAF is a powerful and flexible solution to safeguard your web applications from a wide range of threats. Whether you're deploying a global application through Azure Front Door or hosting services regionally via Application Gateway, integrating WAF should be a core part of your security strategy.

👉 Start today by deploying your first WAF policy and monitoring in detection mode!

📌 Want to Learn More?

Azure WAF Documentation

🔐 A Deep Dive into Azure Web Application Firewall (WAF)