Beyond Prompt Injection: A Developer’s Guide to Multi-Agent Systems Security (MASS)

If you’ve been building with AI lately, you’ve probably noticed the shift. We’re moving fast from single-purpose LLM chatbots to complex Multi-Agent Systems (MAS). These are networks of autonomous agents that talk to each other, use tools, and make decisions on our behalf. But here’s the catch: Securing a network of agents is fundamentally different from securing a single model. Enter Multi-Agent Systems Security (MASS). It’s not just "AI security plus more agents", it’s a specialized discipline focused on the risks that emerge when agents collaborate. In this guide, we’ll break down why traditional security fails in MAS and explore the technical taxonomy of threats you need to watch out for. Why Your Firewall Won't Save Your Agents Traditional security is built on perimeters. You have a database, an API, and a firewall. The logic is static, and the data flows are predictable. MAS shatters this. In a multi-agent ecosystem: Authority is delegated: Agents have "keys" to your tools and da