Each service's mesh sidecar issues short-lived certificates and only accepts an incoming call if the caller proves its identity and is on that service's allow-list — the arrows below are the only calls a service is actually permitted to make.
- Implicit trust — a compromised service can call anything on the internal network; nothing checks who's asking, so the breach reaches every other service almost immediately regardless of which one was popped first.
- mTLS + service mesh — the sidecar rejects any call outside the allow-list even though it originates inside the cluster. The breach can only pivot along real caller→callee edges, so a leaf service with no outgoing permissions contains the damage to itself.