MQTT Security
MQTT security encompasses the practices and configurations needed to protect the Message Queuing Telemetry Transport protocol — a lightweight publish-subscribe messaging standard widely used in IoT — from eavesdropping, unauthorised access, and message manipulation.
MQTT (Message Queuing Telemetry Transport) is a lightweight messaging protocol designed for constrained devices and low-bandwidth, high-latency networks. It operates on a publish-subscribe model where clients connect to a central broker, subscribe to topics, and publish messages. Its simplicity and efficiency have made it the de facto standard for IoT communication, but its default configuration is often insecure.
Out of the box, many MQTT brokers such as Mosquitto allow anonymous connections without authentication or encryption. This means that anyone who can reach the broker on port 1883 can subscribe to all topics and read every message being exchanged, or publish malicious commands to devices. In industrial and smart-home environments, this can lead to serious consequences ranging from data leakage to physical safety hazards.
Securing MQTT requires a layered approach. Transport-layer security (TLS) should be enforced to encrypt all communications between clients and the broker, typically on port 8883. Strong authentication must be configured using username-password pairs, client certificates, or integration with OAuth 2.0 providers. Topic-level access control lists (ACLs) should restrict which clients can publish or subscribe to specific topics. Brokers should be configured to reject anonymous connections and limit payload sizes to prevent denial-of-service attacks.
Regular auditing of broker configurations and monitoring of connected clients are essential for maintaining a secure MQTT deployment in production IoT systems.