Securing MQTT Interfaces with Web Application Firewalls: A Comprehensive Approach to IoT Security

The Message Queuing Telemetry Transport (MQTT) protocol has emerged as a foundational communication protocol in Internet of Things (IoT) deployments due to its lightweight design and publish-subscribe architecture. However, the increasing adoption of MQTT across critical infrastructure, smart cities, and industrial IoT applications has made it an attractive target for malicious actors. This paper presents a novel Web Application Firewall (WAF) architecture specifically designed for MQTT interfaces, offering protection against common attack vectors including Distributed Denial of Service (DDoS) attacks, authentication bypass attempts, message size anomalies, and topic structure exploitation. We propose mathematical models for anomaly detection, develop heuristics for distinguishing between legitimate and malicious traffic patterns, and evaluate our approach using real-world IoT deployments. Our experimental results demonstrate that the proposed MQTT-WAF solution can effectively mitigate up to $99.7 \%$ of malicious traffic while maintaining a false positive rate below $0.3 \%$ and adding minimal latency to legitimate communications.