message-bus-securitylisted

# Message Bus Security Message buses (NATS, RabbitMQ, Kafka, MQTT, AWS SQS/SNS, GCP Pub/Sub) are the connective tissue of distributed systems. They're also the most under-audited part of most architectures — by the time the audit gets to "what's on the bus and who can see it", the team has often been on the system for years without revisiting. This skill is the per-bus and cross-bus checklist. Pairs with [`distributed-system-audit`](../distributed-system-audit/SKILL.md) (system-level audit), [`agent-client-security`](../agent-client-security/SKILL.md) (when agents are producers/consumers). ## When to invoke - Introducing a message bus to a new architecture - Adding multi-tenancy to an existing bus - After an incident involving cross-tenant leakage, replay, or denial-of-service via the bus - Auditing a system that uses a bus, especially distributed-agent / IoT / worker-pool architectures - Periodic review (annually for production buses) ## The model For each bus, you're checking: 1. **Authentication** — who can connect at all 2. **Authorization** — who can publish where, who can subscribe to what 3. **Tenancy** — can tenant A see tenant B's messages, ever 4. **Confidentiality** — in-transit + at-rest encryption 5. **Integrity / replay** — can a captured message be re-sent or forged 6. **Reliability semantics** — exactly-once / at-least-once / at-most-once, and does the application correctly handle the chosen mode 7. **Audit** — when something happens, can you tell who d