Network Security Essentials

Zero Trust Network Architecture

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LearnStep 1 of 3

Implementing Zero Trust in Modern Infrastructure

Learning Objectives

•Deconstruct the core tenets of Zero Trust Architecture (ZTA) and the 'assume breach' mentality
•Implement microsegmentation strategies to restrict lateral movement within distributed systems
•Architect identity-aware access controls leveraging the Google BeyondCorp model
•Secure service-to-service communication using Service Mesh patterns and mTLS

Lesson Outline

LearnStep 1/3

Implementing Zero Trust in Modern Infrastructure

Traditional network security relied on the castle-and-moat analogy: a hardened perimeter (firewalls, VPNs) protecting a trusted internal network. In modern cloud-native environments, this model is obsolete. Zero Trust Architecture (ZTA) operates on the premise that trust is a vulnerability. We must assume the network is already compromised.

The Three Pillars of Zero Trust

Verify Explicitly: Never authenticate based on network location (IP address). Always authenticate and authorize based on all available data points: user identity, location, device health, service classification, and anomalies.
Use Least Privilege Access: Limit user access with Just-In-Time and Just-Enough-Access (JIT/JEA), risk-based adaptive polices, and data protection.
Assume Breach: Minimize blast radius and segment access. Verify end-to-end encryption and use analytics to get visibility, drive threat detection, and improve defenses.

Google BeyondCorp Model

BeyondCorp is Google's implementation of Zero Trust. It shifts access controls from the network perimeter to individual devices and users. Access to tools depends on the credentials of the user and the status of the device (is it managed? is the OS patched?).

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Microsegmentation and Service Mesh

In Kubernetes and microservices, Zero Trust is often implemented via a Service Mesh (like Istio or Linkerd). The mesh injects a sidecar proxy (Envoy) next to every container.

Key capabilities:

mTLS (Mutual TLS): Both the client and server validate each other's certificates. This encrypts traffic and provides cryptographic identity to every workload.
Authorization Policies: Fine-grained control over which services can talk to which.

Example: Locking down a Payment Service

By default, Kubernetes allows all pod-to-pod traffic. Here is how we restrict access using an Istio AuthorizationPolicy so that only the frontend service can call the payment service.

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