A retailer's public web application is suffering automated attacks attempting SQL injection and cross-site scripting against its HTTP endpoints, and the design must inspect and filter malicious application-layer requests against common web exploits before they reach the application. The architect needs the control purpose-built to block layer-7 web attacks at the network edge. Which control should the design place in front of the application?
- AA network security group on the application subnet configured to permit only the load balancer's address range to reach the web servers on the HTTP and HTTPS ports.
- BAzure DDoS Protection on the public address so that volumetric and protocol floods aimed at the application are absorbed and mitigated before they degrade availability.
- CMicrosoft Defender for Cloud workload protection on the web servers so that suspicious process behaviour on the hosts is detected and alerted to the security team.
- DAzure Web Application Firewall with the managed rule set so that layer-7 requests are inspected and known web exploit patterns are blocked before reaching the application. Correct
Why A is wrong: A network security group restricts traffic by address and port and is a reasonable hygiene control, but it operates at layers 3 and 4 and cannot read request payloads, so it cannot detect or block the injection and scripting attacks the requirement describes.
Why B is wrong: DDoS Protection defends availability against floods and is tempting because the traffic is attacker-driven, but it targets volumetric and protocol abuse rather than malicious request content, so it does nothing against injection or cross-site scripting payloads.
Why C is wrong: Host workload protection detects malicious behaviour after a request lands and is appealing as defence in depth, but it alerts on host activity rather than filtering inbound web requests, so it does not block layer-7 exploits at the edge as required.
Why D is correct: Azure Web Application Firewall inspects HTTP request content at layer 7 and applies managed rules that block injection and cross-site scripting before traffic reaches the application, which is the purpose-built edge control the requirement specifies.