In this Certified Kubernetes Security Specialist (CKS) Exam study guide, I have listed all the resources you can use to pass the CKS certification exam.
What Is the Certified Kubernetes Security Specialist Exam?
CKS is one of the best Kubernetes Certifications that is focused on the security aspects of Kubernetes.
The official CNCF certification page says,
The Certified Kubernetes Security Specialist (CKS) program provides assurance that a CKS has the skills, knowledge, and competence on a broad range of best practices for securing container-based applications and Kubernetes platforms during build, deployment, and runtime.
The CKS exam curriculum is well structured, with topics related to Kubernetes security. In fact, you can use the curriculum as a checklist for your existing Kubernetes implementations.
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Your first step towards CKS Certification is registering for the exam on the Linux Foundation portal. When you register you get free access to two sessions of killer.sh CKS practice exams that will help you clear the CKAD exam.
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Certified Kubernetes Security Specialist (CKS) Exam Preparation Guide
We will look at the detailed CKS resources list and links to the official documentation you could use during the CKS exam.
CKS Guide Topics
CKS Exam Prerequisites
The only prerequisite is that you should have a valid CKA certification to sit for the CKS Exam.
If you have not passed the CKA exam, refer to our CKA exam guide for all useful resources.
Even if you don’t have the CKA certification, you can purchase the CKS exam as a bundle (CKA + CKS). You can save up to $206 using the bundle with an additional 21% discount. However, you need to first pass the CKS and then you can appear for the CKS exam.
CKS Exam Details
Following is the important information about CKS Exam.
|Exam Duration||2 hrs|
|CKS Validity||2 Years|
|CKS Certification Exam Cost||$375|
As CKS is an open book exam, you can use the following Kubernetes and third-party tools documentation that is part of the CKS exam.
Allowed Third-Party Tools & Documentation for CKS exam
Important Note: The following domains are allowed in the exam. However, you are not allowed to visit any other domains that are mentioned in the documents.
Please refer to the official Kubernetes exam FAQ section for more details
CKS Exam Syllabus
CKS Exam aims to test your skills on different security aspects. The following table shows the different domains and their weightage for the CKS certification.
|Minimize Microservice Vulnerabilities||20%|
|Supply Chain Security||20%|
|Monitoring, Logging, and Runtime Security||20%|
Certified Kubernetes Security Specialist Certification Courses
If you want to sign up for a course for your CKS preparation, the following are the courses you will ever need.
Both authors have done a great job creating the course content with good practice labs.
Kubernetes Security Books
Following are the Kubernetes books related to security you can use of CKS preparation.
Setting up CKS Practice Labs
It would be best to have a practice cluster to learn and try out all the concepts involved in CKS certification. I have the following suggestion for CKS practice labs.
- Kubernetes Setup using Kubeadm [Detailed Guide]
- Kubernetes Vagrant Setup using Kubeadm
- GKE Cluster using free Google Cloud Credits
- EKS Service on AWS using Free tier program
- AKS service on Azure using free cloud credits
- Kubernetes Cluster on Digital Ocean[ Get $100 Digital Ocean Free Credits]
Note: To get notification on the above-mentioned setup and other CKS tutorial articles, Signup to the CKS newsletter
CKS Syllabus Wise Resources
Let’s have a look at the official syllabus-wise resources for the CKS exam. All the topics mentioned are as per the official Linux Foundation Certified Kubernetes Security Specialist Exam Syllabus.
Cluster Setup [10%]
Under cluster setup, the focus is more on the security aspects of the cluster components. This section carries 10% weightage in the CKS questions.
Kubernetes Network Policies
By default, when you set up a Kubernetes cluster, pods in all the namespaces can talk to each other.
This is not a secure setup because you might be running a different type of workload in a cluster that requires isolation in terms of networking.
Kubernetes network policies help you to enable rules for pod network communication.
|Use Network security policies to restrict cluster level access||Kubernetes Network Security Policy Documentation|
|Associated Task||Declaring Kubernetes Network Policy|
|Network Policy Editor||editor.cilium.io|
Kubernetes CIS benchmark
Center for Internet Security (CIS) with the Kubernetes community has created the benchmarks for Kubernetes security standards.
Organizations can use the Kubernetes CIS benchmarks to achieve security and compliance requirements.
If you want to know more about CIS, please read CIS FAQ’s
See Kubernetes CIS benchmark to download the latest CIS benchmarks for kubernetes.
Kube-bench is an open-source utility maintained by Aquasec to run all the CIS benchmark checks against a Kubernetes cluster.
|Use CIS benchmark to review the security configuration of Kubernetes components (etcd, kubelet, kubedns, kubeapi)||CIS Kubernetes benchmark using Kube-bench|
From a security standpoint, for Ingress, the primary focus is on configuring ingress with TLS configurations
Also, it would help if you looked at setting up the namespace scoped and cluster-wide ingress.
You should also look at setting up multiple ingress/ingress controllers using the Ingressclass
|Properly set up Ingress objects with security control||Ingress documentation|
|Understanding Ingress||The complete ingress guide|
|Understanding Ingress controller||Nginx ingress controller setup guide|
Kubernetes Node Metadata & Endpoints
Metadata concealment is required for a cloud-based Kubernetes setup where the instances expose the instance metadata information, including credentials.
This means the pods running on each instance would have access to the metadata server endpoint to retrieve information.
Pod’s access to the Metadata server can be controlled via Network policies.
|Protect node metadata and endpoints||Restricting cloud metadata API access|
|Configuring Network Policies||Guide to configure network policies|
Note: When you use managed Kubernetes services on the cloud (GKE, EKS, AKS), it comes with options to disable metadata access for pods.
Securing Kubernetes GUI
It is essential to secure Kubernetes dashboard access as it is accessed by cluster users from different networks in an organization. Also, many Kubernetes hacking incidents happened due to the wrong security configurations of the Kubernetes dashboard.
You need to learn all the best practices and configurations involved in setting up a secure Kubernetes dashboard. For example, limiting access to the dashboard with specific internal networks, user access with limited privileges to the dashboards, etc.
|Minimize use of, and access to, GUI elements||Kubernetes Web UI Configurations|
|Blog on Securing Kubernetes Dashboard||How to Secure Kubernetes Dashboard|
Verify platform binaries before deploying
Learn to verify the Kubernetes binaries using the checksum. The kubernetes Github release page has the version numbers and SHA ids to verify the binary.
|Kubernetes Binaries||Github Kubernetes Releases|
Cluster Hardening [15%]
Kubernetes Cluster Hardening carries 15% weightage in the CKS exam. Let’s have a look at the individual concepts under cluster hardening.
Restrict access to Kubernetes API
Restricting API access is very important when it comes to Kubernetes Production Implementation. Third-party services and services running inside the cluster should access the Kubernetes API with only required privileges.
The primary topics under this section would be bootstrap tokens, RBAC, ABAC, service account, and admission webhooks.
|Cluster API access methods||Ways to access Kubernetes cluster API|
|Kubernetes API Access Security||Controlling access to Kubernetes API|
|Authentication||Kubernetes Authentication Overview|
|Authorization||Kubernetes Authorization Overview|
|Admission Controllers||Admission Controllers Overview|
|Admission Webhooks||Admission Webhooks Overview|
|Certificates||Certificate Signing Requests Overview|
|Note Authorization||Node Authorization Overview|
|Task||Accessing Kubernetes API from a Pod|
Use Role-Based Access Controls to minimize exposure
With Kubernetes RBAC, you can define fine-grained control on who can access the Kubernetes API to enforce the principle of least privilege. Allowing unnecessary cluster-wide access to everyone is a common mistake done during Kubernetes implementations.
Two main concepts in RBAC are,
- Role: List of allowed API access
- RoleBinding – Binding a role to a user, group, or service account.
|Roles, ClusterRoles, RoleBindings and ClusterRoleBindings||RBAC detailed documentation|
Exercise caution in using service accounts e.g., disable defaults, minimize permissions on newly created ones.
Service accounts are the best way to provide access to application/pods which require Kubernetes API access.
Every namespace has a default service account, and it gets attached to the pod if you don’t specify any service account explicitly. The default service account does not have any privileges. But if you bind a role to it, it will get all the access listed in the role, and it applies to all the pods in the namespace.
Standard practice is to deploy different workloads with different service accounts to enforce the principle of least privilege.
Update Kubernetes frequently
Whenever you upgrade a Kubernetes cluster, you should follow the recommended practices to make sure you have the application’s availability.
Also, you should have mechanisms to validate the cluster components, security configurations, and application status post-upgrade.
System Hardening [15%]
System hardening aims at reducing vulnerabilities in applications and infrastructure components that reduce the attack surface.
The common system hardening activities are
- Applying timely patches
- Removing all non-essential utilities
- Limiting access with firewall rules and utilities.
- Logging all system activities.
When it comes to CKS, we have the following list of system hardening activities.
Minimize host OS footprint (reduce attack surface)
- Removing unwanted binaries and services that are not required for cluster operation.
- Adding correct firewall rules to restrict host access on opened ports
- Containers should have fewer privileges on the host OS. Run container as a non-root user
|Restricting Kernel Modules||Preventing Container Loading unwanted Kernel modules|
Minimize IAM roles
This is to achieve the principle of least privilege.
Refer topic related to RBAC for role-related concepts. Normally IAM is applicable for cloud implementations that integrate with kubernetes RBAC
Minimize external access to the network
Loadbalancer is a common component that allowed external access for the Kubernetes cluster.
|Loadbalancer Access Restriction||Restrict Loadbalancer access from external networks|
Appropriately use kernel hardening tools such as AppArmor, seccomp
AppArmor (“Application Armor”) is a Linux kernel security module that allows the system administrator to restrict programs’ capabilities with per-program profiles.
AppArmor is part of the official CKS allowed documentation.
|AppArmor||Restrict a Container’s Access to Resources with AppArmor|
|Seccomp||Restrict a Container’s Syscalls with Seccomp|
|Task||Securing a Pod Using Apparmor|
|Task||Set the Seccomp Profile for a Container|
Minimize Microservice Vulnerabilities [20%]
As the title suggests, this section is more about service-to-service communications. You need to learn all the core concepts and Kubernetes objects involved in securing communication between pods.
Setup appropriate OS-level security domains e.g. using PSP, OPA, security contexts
PSP is getting deprecated from Kubernetes version V1.21. But it is a good topic from a learning perspective.
Open Policy Agent is a great utility for implementing fine-grained controls for microservices.
|PSP||Pod Security Policy|
|OPA||OPA Gatekeeper: Policy and Governance for Kubernetes|
|Security Context Task||Configure a Security Context for a Pod or Container|
Manage Kubernetes secrets
Kubernetes secret is one of the ways to save sensitive information inside the pod. But, it is not encrypted. It is saved in a base64 encoded format. However, you can encrypt the data at rest.
Use container runtime sandboxes in multi-tenant environments (e.g. gvisor, kata containers)
|Pod Security Standards||Sandboxed Pods|
|Workload Isolation||Workload Isolation using gVisor and kata containers|
Implement pod to pod encryption by use of mTLS
There is no documentation on enabling mTLS between pods. However, you can use the kubernetes
certificates.k8s.io API to generate certificates to use in the pod to pod encryption.
For example, if you have two java services, you can convert the certificates you generate from the certificate API and convert it to JKS format using keytool and enable the pod to pod encryption with java settings.
|Task: Generating TLS Certificate||Manage TLS Certificates in a Cluster|
Supply Chain Security [20%]
Minimize base image footprint
There is no specific documentation on base image optimization on kubernetes.io. However, you can use the following blog for learning purposes.
|Base Image Optimisation||Top 20 Dockerfile best practices|
Secure your supply chain: whitelist allowed registries, sign and validate images
It’s important to verify the pulled base images are from valid sources. This can be achieved using
ImagePolicyWebhook admission controller.
|ImagePolicyWebhook||Using ImagePolicyWebhook Admission Controller|
Use static analysis of user workloads (e.g.Kubernetes resources, Docker files)
|Static analysis of user workloads||Statically Analyse YAML|
Scan images for known vulnerabilities
Aquasec trivy is recommended in the Kubernetes CKS exam documentation. You can use Trivy to scan images for vulnerabilities.
Monitoring, Logging and Runtime Security [20%]
Perform behavioral analytics of syscall process and file activities at the host and container level to detect malicious activities
|Syscalls with Seccomp||Restrict a Container’s Syscalls with Seccomp|
Detect threats within a physical infrastructure, apps, networks, data, users, and workloads
Falco is the Kubernetes threat detection engine. It can alert find unexpected application behavior and alert threats on time.
|Threat detection||Using Falco for threat detection|
Detect all phases of attack regardless of where it occurs and how it spreads
Falco might help here. Need to study more about it.
Perform deep analytical investigation and identification of bad actors within the environment
Audit logging helps investigate issues in Kubernetes.
|Investigation||Implementing Kubernetes Auditing|
Ensure immutability of containers at runtime
You can make the pods immutable by making everything the pod uses ReadOnly. For example, read-only filesystem, configmaps, and secrets.
|Immutable file system||PSP readOnlyRootFilesystem|
Use Audit Logs to monitor access
Audit logs capture all the events associated with Kubernetes objects. The audit logs can be used by the monitoring systems to create alerts for unexpected actions.
|Kubernetes Auditing||Enabling Kubernetes Auditing|
CKS is one of the sought-after certifications for aspiring DevOps engineers.
This is the ultimate guide to the Certified Kubernetes Security Specialist exam (CKS). I have covered the most important resources required to ace the CKS exam
If you plan to do the CKS certification, you should not aim to pass the certification with practice exams and exam dumps.
It would really help if you focused on learning all the core Kubernetes Security-related concepts, industry use cases, and best practices.
I will constantly be updating this CKS exam guide with useful resources and tips to pass the CKS exam.
Also, If you are interested in DevOps certifications, check out our comprehensive guide on the best devops certifications.