CKS Minimize Microservice Vulnerabilities Practice Question
Which Istio resource is used to enforce mutual TLS (mTLS) for all services in a namespace, ensuring that traffic between services is encrypted?
⚠ Common exam trap
A common mistake on the CKS exam is confusing PeerAuthentication (which enforces mTLS at the service-to-service level) with DestinationRule (which configures TLS settings for upstream connections but does not enforce authentication). Candidates often choose DestinationRule when they see 'TLS' in the option.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
PeerAuthentication
PeerAuthentication is the correct Istio resource for enforcing mutual TLS (mTLS) at the namespace level. It defines the TLS mode for traffic between services, and when set to `STRICT`, it requires that all traffic within the namespace uses mTLS, encrypting both the request and response. This is part of Istio's security features under the `security.istio.io/v1beta1` API group.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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DestinationRule
Why it's wrong here
DestinationRule is a traffic-management API that controls load balancing, connection pool, and TLS settings for upstream hosts. While it can set client-side TLS context (e.g., for originating mutual TLS to external services), it does not enforce mTLS on workloads within the mesh. mTLS enforcement is a server-side policy, which belongs to PeerAuthentication, not DestinationRule.
- ✓
PeerAuthentication
Why this is correct
PeerAuthentication is the Istio security resource that defines mTLS policy for workloads, supporting mesh-wide, namespace-wide, and workload-specific scopes. Setting 'mode: STRICT' requires all incoming connections to use mutual TLS, and the Envoy sidecars enforce this policy at the server end. This is the correct resource for enforcing mTLS in the mesh.
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ServiceEntry
Why it's wrong here
ServiceEntry is used to add external or non-registered services to Istio's service registry, enabling traffic management and observability for those destinations. It is a discovery/routing resource and contains no fields for authentication, TLS modes, or credential validation. Thus, it cannot enforce mutual TLS.
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VirtualService
Why it's wrong here
VirtualService defines routing rules for traffic between services, such as URI-based forwarding, header matching, and traffic weight shifting. It is purely a traffic-management construct and does not include any authentication or mTLS enforcement options. Security policies like mTLS are handled by separate resources like PeerAuthentication.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CKS practice question is part of Courseiva's free CNCF certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CKS exam.