3.4. Public Access Security

💡 First Principle: Sometimes resources must be publicly accessible—web applications, APIs, CDN content. When you can't hide behind private networks, you must defend with multiple security layers: filtering attacks before they reach your applications.

Think of it like a medieval castle with concentric defenses. The outer walls (DDoS Protection) absorb siege weapons. The inner walls (WAF) catch infiltrators. The gate guards (Azure Firewall) control who enters and exits. No single layer is impenetrable, but together they make attack extremely costly.

What breaks without public access security? Your web applications become sitting ducks. DDoS attacks overwhelm your infrastructure. SQL injection exploits steal your data. Malicious bots scrape your content and abuse your APIs. The internet is a hostile environment, and any publicly exposed service will be attacked—usually within hours of going live.

Consider defense-in-depth: Each tool has a specific purpose. WAF protects against application-layer attacks but cannot stop volumetric DDoS. DDoS Protection handles flood attacks but cannot inspect HTTP payloads. Azure Firewall controls east-west traffic but doesn't understand web application vulnerabilities. The exam tests your ability to select and combine the right tools.