Kubernetes Security Hardening Playbook

The Problem and Why It Mattered

I built a comprehensive GKE security hardening reference implementation — RBAC design, pod security, network segmentation, admission control, and runtime threat detection, all codified in Terraform and Kubernetes manifests. The relevant technical and business risk is the cost of leaving this workflow, control, or product boundary unclear, manual, insecure, or difficult to operate. The case study focuses on the decisions used to make that risk manageable.

Objectives and Success Criteria

• Deliver the capability described in the project objective using a maintainable technical design.
• Make the main workflow, control boundary, and operational responsibilities explicit.
• Produce reviewable implementation evidence without publishing confidential values or customer data.

Requirements and Constraints

The delivery design had to be repeatable across environments, minimise direct production access, and retain enough evidence to investigate and roll back change safely.

My Role and Ownership

I owned the technical design and implementation described in this portfolio record, including the technology choices, core system boundaries, and the documentation of the resulting approach. Related organisational decisions, vendor operations, and formal certification decisions remain outside the scope of this technical case study unless stated explicitly.

Solution Overview

The solution is built around GKE, OPA Gatekeeper, Kyverno. Its implementation is organised as the components below so that the architecture, control points, and operating model can be evaluated separately rather than treated as a list of tools.

Architecture and System Design

The public architecture description follows the path from the initiating user, workload, or operator action through the relevant devsecops components. Access boundaries, data or state handling, and operational controls are described at a safe level; secrets, private addresses, and client-sensitive implementation details are intentionally omitted.

Technology Decisions and Trade-Offs

I selected GKE, OPA Gatekeeper, Kyverno because they support the project objective and make the critical engineering boundaries explicit. The trade-off is operational and platform complexity: the design depends on documented configuration, controlled access, and ongoing review rather than assuming that a managed service or framework removes engineering responsibility.

Implementation Walkthrough

The following implementation notes describe the components that matter most to the project outcome. They are intentionally focused on technical decisions and operating behaviour instead of reproducing entire source files or sensitive configuration.

Implementation: RBAC Design — Least Privilege

Four roles: cluster-admin (break-glass service account only), namespace-admin, developer (deploy and logs — no secret access, no RBAC modification), and read-only. A Kyverno policy blocks any ClusterRoleBinding referencing a human user email.

Implementation: Pod Security Standards — Restricted

Restricted PodSecurity enforced at the namespace level: no privileged containers, no host path mounts, no host network or PID sharing, containers running as non-root with a non-zero UID, all capabilities dropped, seccomp profiles set to RuntimeDefault.

Implementation: OPA Gatekeeper Policies

Constraint library covering: required resource requests and limits on all containers; prohibited image registries (Artifact Registry only); required labels on all workloads; prohibited hostPath volumes and hostNetwork settings.

Implementation: Network Policy — Default Deny

Default-deny-all NetworkPolicy in every namespace, with explicit whitelisting of only required pod-to-pod and pod-to-external communication. Cilium's network policy visualiser used to verify no unintended traffic paths exist.

Implementation: Runtime Threat Detection with Falco

Falco deployed as a DaemonSet with custom rules targeting container escape techniques, cryptocurrency mining patterns, unexpected outbound connections, and shell execution inside containers that should never have a shell. Alerts route to Chronicle SIEM.

Implementation: GKE-Specific Hardening

Shielded GKE Nodes (Secure Boot + vTPM + Integrity Monitoring), Workload Identity enabled, private cluster (no public node IPs), Binary Authorization policy requiring signed images.

Challenges, Failures and Corrections

This portfolio record does not invent deployment failures, client incidents, or corrective actions that are not supported by the published project evidence. Where operational details are confidential or were not captured for public release, the case study documents the design boundary and lesson instead of presenting an unsupported narrative.

Security, Compliance and Risk

The public record avoids secrets, customer data, and private infrastructure details. The relevant security controls, access boundaries, and operational risks are addressed in the implementation notes where they are material to the project.

Testing, Validation and Evidence

The evidence published for this project is the documented implementation, its stated architecture and controls, and the portfolio record. The published record documents the implemented architecture, the core controls, and the technology choices that can be reviewed without exposing confidential operational data. Claims are limited to the implementation details and outcomes documented in this case study.

Results and Evidence

The published record documents the implemented architecture, the core controls, and the technology choices that can be reviewed without exposing confidential operational data.

What I Learned

This project reinforced that devsecops work is not a technology checklist. The durable value comes from making boundaries, trade-offs, ownership, and evidence clear enough for another engineer or stakeholder to review and operate the system responsibly.

What I Would Improve Next

• Expand automated validation around the most important workflow and control boundaries.
• Add or deepen operational evidence, such as dashboards, test artefacts, or an architecture diagram where it is safe to publish one.
• Review the design against the next expected scale, reliability, and governance requirement before extending the system.

Final Takeaway

This devops and platform engineering case study addresses a defined technical problem through GKE, OPA Gatekeeper, Kyverno. It demonstrates my ability to turn requirements into an explainable design, implement the important controls, and document outcomes and limitations without overstating what the evidence proves.