seikaikyo/benchmarking-kubernetes-with-kube-bench

Benchmarking Kubernetes with kube-bench

Overview

kube-bench (by Aqua Security) is an open-source tool that checks whether a Kubernetes cluster is deployed securely by running the checks documented in the CIS Kubernetes Benchmark. It inspects the control-plane components (API server, controller manager, scheduler, etcd), the kubelet and worker-node configuration, and cluster-wide policy settings, then reports each check as PASS, FAIL, WARN, or INFO with a remediation recommendation drawn directly from the CIS guidance. Tests are configuration-driven YAML files, so kube-bench tracks new Kubernetes versions and benchmark revisions and supports managed distributions (EKS, GKE, AKS, ACK, OpenShift, RKE, k3s).

Hardening a cluster against the CIS Benchmark directly reduces the attack surface for T1610 (Deploy Container), where an adversary deploys a container to execute code or evade defenses — for example by abusing privileged containers, host namespaces, anonymous API access, or insecure kubelet settings that an unhardened cluster leaves exposed.

kube-bench can run as a standalone binary on a node, inside a container, or — most commonly — as a Kubernetes Job whose pod has the host filesystem mounted so it can read the relevant config files. Output is available as human-readable text, JSON, JUnit, or AWS Security Finding Format (ASFF) and can be pushed to a PostgreSQL database for trend tracking.

When to Use

• When establishing a security baseline for a new Kubernetes cluster against the CIS Kubernetes Benchmark.
• When performing periodic compliance audits of control-plane and node hardening.
• When validating remediation after applying hardening changes (re-run to confirm checks now PASS).
• When integrating cluster compliance scanning into CI/CD or a continuous monitoring pipeline.
• When preparing evidence for SOC 2, PCI DSS, or internal hardening compliance.

Prerequisites

• Access to the cluster: either SSH access to a control-plane/worker node (binary mode) or kubectl with permission to create Jobs (in-cluster mode).
• Knowledge of the cluster's Kubernetes version (kube-bench auto-detects, or specify with --version / --benchmark).
• Install kube-bench (Aqua Security official methods):

# Binary release (Linux)
KB_VERSION=0.10.7
curl -L -o kube-bench.tgz \
  "https://github.com/aquasecurity/kube-bench/releases/download/v${KB_VERSION}/kube-bench_${KB_VERSION}_linux_amd64.tar.gz"
tar -xzf kube-bench.tgz
sudo mv kube-bench /usr/local/bin/
sudo cp -R cfg /etc/kube-bench/cfg

# Via Go install
go install github.com/aquasecurity/kube-bench@latest

# Run as a one-off container directly on a node (mounts host config)
docker run --rm --pid=host \
  -v /etc:/etc:ro -v /var:/var:ro \
  -t docker.io/aquasec/kube-bench:latest run --targets node

# Verify
kube-bench version

Objectives

• Run kube-bench against the appropriate benchmark for the cluster's Kubernetes version.
• Scan control-plane (master), node, etcd, control-plane policies, and managed-service targets.
• Produce machine-readable JSON/JUnit output for pipelines and dashboards.
• Triage FAIL and WARN results and apply CIS remediation guidance.
• Re-run to validate that remediations now PASS.

MITRE ATT&CK Mapping

| Technique ID | Name | Tactic | Relevance | |--------------|------|--------|-----------| | T1610 | Deploy Container | Execution / Defense Evasion | CIS Benchmark hardening enforced by kube-bench restricts privileged/host-namespace deployments, anonymous API access, and insecure kubelet settings that adversaries abuse when deploying malicious containers. |

Workflow

1. Run the default scan (auto-detect)

Run all applicable targets, letting kube-bench detect the Kubernetes version and benchmark:

sudo kube-bench

2. Run as a Kubernetes Job (in-cluster)

Apply the provided Job manifest from the kube-bench repo and read the results from the pod logs:

# General-purpose job
kubectl apply -f https://raw.githubusercontent.com/aquasecurity/kube-bench/main/job.yaml

# Wait, then retrieve results
kubectl get pods -l app=kube-bench
kubectl logs -l app=kube-bench

# Platform-specific jobs are available, e.g. EKS:
kubectl apply -f https://raw.githubusercontent.com/aquasecurity/kube-bench/main/job-eks.yaml

3. Target specific components

Use run --targets to scope the scan to particular component groups:

# Control-plane (API server, scheduler, controller manager)
sudo kube-bench run --targets master

# Worker node (kubelet, proxy)
sudo kube-bench run --targets node

# etcd datastore
sudo kube-bench run --targets etcd

# Cluster-wide policies (RBAC, pod security, network policy)
sudo kube-bench run --targets policies

# Combine multiple targets
sudo kube-bench run --targets master,node,etcd,policies

4. Pin a specific benchmark or Kubernetes version

When auto-detection is wrong or you must audit against a specific revision, pin the benchmark explicitly:

# Pin to a specific CIS benchmark revision
sudo kube-bench run --benchmark cis-1.8

# Or map by Kubernetes version
sudo kube-bench --version 1.27

# Managed/distribution-specific benchmarks
sudo kube-bench run --benchmark eks-1.5.0
sudo kube-bench run --benchmark gke-1.6.0
sudo kube-bench run --benchmark rke2-cis-1.7

5. Run or skip individual checks

Focus on or exclude specific check IDs during remediation cycles:

# Run only specific checks
sudo kube-bench run --targets master --check 1.2.1,1.2.2

# Skip noisy/known-accepted checks
sudo kube-bench run --targets node --skip 4.2.6

6. Produce machine-readable output

Emit JSON or JUnit for ingestion into pipelines, SIEM, or dashboards, and write to a file:

# JSON to a file
sudo kube-bench run --targets master,node --json --outputfile kube-bench-report.json

# JUnit (for CI test reporting)
sudo kube-bench --junit --outputfile kube-bench-junit.xml

# AWS Security Finding Format (for Security Hub)
sudo kube-bench run --targets node --asff

7. Triage and remediate FAIL/WARN findings

Each failing check prints a remediation. Apply the CIS-recommended fix on the node/manifest, for example tightening API server flags in the static pod manifest:

# Example remediation for a common control-plane FAIL:
# CIS 1.2.x — ensure anonymous-auth is disabled on the API server.
# Edit the static pod manifest and set the flag:
sudo vi /etc/kubernetes/manifests/kube-apiserver.yaml
#   - --anonymous-auth=false
# The kubelet restarts the static pod automatically.

# Example node remediation — kubelet config file permissions (CIS 4.1.x):
sudo chmod 600 /etc/kubernetes/kubelet/kubelet-config.json
sudo chown root:root /etc/kubernetes/kubelet/kubelet-config.json

8. Re-validate after remediation

Re-run the relevant target and confirm the previously failing checks now PASS, then track the score over time:

sudo kube-bench run --targets master --check 1.2.1 --json --outputfile recheck.json

# Optional: persist results to PostgreSQL for trend tracking
sudo kube-bench run --targets master,node --pgsql

Tools and Resources

| Tool / Resource | Purpose | Link | |------------------|---------|------| | kube-bench | CIS Kubernetes Benchmark checker | https://github.com/aquasecurity/kube-bench | | kube-bench docs | Running / platforms / flags | https://aquasecurity.github.io/kube-bench/ | | CIS Kubernetes Benchmark | Source hardening standard | https://www.cisecurity.org/benchmark/kubernetes | | Trivy Operator | Continuous in-cluster compliance + vuln scanning | https://github.com/aquasecurity/trivy-operator | | kube-hunter | Complementary penetration-testing tool | https://github.com/aquasecurity/kube-hunter |

Validation Criteria

• [ ] kube-bench installed (kube-bench version) or running as a Job.
• [ ] Scan run against the correct benchmark for the cluster's Kubernetes version.
• [ ] master, node, etcd, and policies targets each scanned.
• [ ] JSON/JUnit output produced for pipeline/dashboard ingestion.
• [ ] FAIL and WARN findings triaged and prioritized.
• [ ] CIS remediation applied to control-plane manifests and node configs.
• [ ] Re-run confirms previously failing checks now PASS.
• [ ] Results tracked over time (file archive or PostgreSQL).