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Agent skill

Implementing Network Policies For Kubernetes

by mukul975 in mukul975/Anthropic-Cybersecurity-Skills

Writes portable upstream Kubernetes NetworkPolicy YAML - default-deny-all, DNS egress, namespace and pod selector rules - that works on any conformant CNI such as Calico or Cilium.

Apache-2.0Auto-check passedDevOps & Cloud

Install Implementing Network Policies For Kubernetes

skills CLI
$ npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill implementing-network-policies-for-kubernetes -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install mukul975/Anthropic-Cybersecurity-Skills implementing-network-policies-for-kubernetes --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/mukul975/Anthropic-Cybersecurity-Skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/implementing-network-policies-for-kubernetes .claude/skills/implementing-network-policies-for-kubernetes && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
implementing-network-policies-for-kubernetes
GitHub stars
34k
Token cost
~1.5k tokens
SKILL.md length
158 words
Files
8 (incl. scripts, references, assets)
Skills in repo
644
Repo updated
First seen
Licence
Apache-2.0

At a glance

Writes portable upstream Kubernetes NetworkPolicy YAML - default-deny-all, DNS egress, namespace and pod selector rules - that works on any conformant CNI such as Calico or Cilium.

  • Works in 6 steps: Default Deny All Traffic → Allow DNS Egress (Required for Service… → Application-Specific Policies → …
  • Segmentation must stay CNI-portable
  • SKILL.md covers Overview, When to Use, Prerequisites and Workflow, plus 2 more sections
  • Runs Python scripts from its folder; calls kubectl

What it does

Implementing Network Policies For Kubernetes is an agent skill from mukul975/Anthropic-Cybersecurity-Skills. Writes portable upstream Kubernetes NetworkPolicy YAML - default-deny-all, DNS egress, namespace and pod selector rules - that works on any conformant CNI such as Calico or Cilium. Use when segmentation must stay CNI-portable, introducing a default-deny posture, or restricting east-west traffic between pods and namespaces without depending on a vendor CRD. Keywords: NetworkPolicy, default deny, podSelector, namespaceSelector, ingress, egress, CNI portable. Do not use for Calico-specific resources - use…

Its SKILL.md is about 1.5k tokens, which your agent loads only when the skill is triggered. The skill folder holds 10 other files, including scripts, reference files and assets (for example `assets/template.md`, `references/api-reference.md` and `references/standards.md`).

It sits in DevOps & Cloud, covering Container orchestration and Cloud networking. It works with Kubernetes. The repository describes itself as: 817 structured cybersecurity skills for AI agents · Mapped to 6 frameworks: MITRE ATT&CK, NIST CSF 2.0, MITRE ATLAS, D3FEND, NIST AI RMF & MITRE F3 (Fight Fraud) · agentskills.io…. The licence is Apache-2.0.

When your agent uses it

  • Segmentation must stay CNI-portable
  • Introducing a default-deny posture
  • Restricting east-west traffic between pods and namespaces without depending on a vendor CRD
  • Calico-specific resources - use implementing-kubernetes-network-policy-with-calico

Example prompts

  • “Use the implementing-network-policies-for-kubernetes skill to write portable upstream Kubernetes NetworkPolicy YAML - default-deny-all, DNS egress…”
  • “/implementing-network-policies-for-kubernetes”

Requirements

  • Python 3

Workflow steps

6 steps, taken from the step headings in SKILL.md.

  1. Default Deny All Traffic
  2. Allow DNS Egress (Required for Service Discovery)
  3. Application-Specific Policies
  4. Cross-Namespace Policies
  5. Egress Restrictions
  6. Block Cloud Metadata Access

What it can do on your machine

Read from SKILL.md and the folder at commit 54a7988. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Ships 2 files in scripts/ (Python), which the agent can run.

    Shell commands in SKILL.md call:

    • kubectl

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • kubernetes.io
    • docs.tigera.io
    • docs.cilium.io
    • editor.networkpolicy.io

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Implementing Network Policies For Kubernetes loads about 1.5k tokens when it runs, and up to ~2.3k if it reads all its reference files. Until then it costs about 151 tokens; SKILL.md has 158 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~151
When it runs · the whole SKILL.md, loaded when a task matches
~1.5k
With references · SKILL.md plus every file in references/, read only if the agent opens them
~2.3k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

The full file from mukul975/Anthropic-Cybersecurity-Skills at commit 54a7988, republished under its Apache-2.0 licence (© mukul975). 158 words, ~1,507 tokens.

Download SKILL.mdSave it as .claude/skills/implementing-network-policies-for-kubernetes/SKILL.md (or your agent's skills folder). This skill also uses 7 other files; get the full folder from GitHub.
name
implementing-network-policies-for-kubernetes
description
Writes portable upstream Kubernetes NetworkPolicy YAML - default-deny-all, DNS egress, namespace and pod selector rules - that works on any conformant CNI such as Calico or Cilium. Use when segmentation must stay CNI-portable, introducing a default-deny posture, or restricting east-west traffic between pods and namespaces without depending on a vendor CRD. Keywords: NetworkPolicy, default deny, podSelector, namespaceSelector, ingress, egress, CNI portable. Do not use for Calico-specific resources - use implementing-kubernetes-network-policy-with-calico.
domain
cybersecurity
subdomain
container-security
tags
containers, kubernetes, security, network-policies, microsegmentation
version
1.0
author
mahipal
license
Apache-2.0
nist_csf
PR.PS-01, PR.IR-01, ID.AM-08, DE.CM-01
mitre_attack
T1610, T1611, T1609, T1525

Implementing Network Policies for Kubernetes

Overview

Kubernetes NetworkPolicies provide pod-level network segmentation by defining ingress and egress rules that control traffic flow between pods, namespaces, and external endpoints. Combined with CNI plugins like Calico or Cilium, network policies enforce zero-trust microsegmentation to prevent lateral movement within the cluster.

When to Use

  • When deploying or configuring implementing network policies for kubernetes capabilities in your environment
  • When establishing security controls aligned to compliance requirements
  • When building or improving security architecture for this domain
  • When conducting security assessments that require this implementation

Prerequisites

  • Kubernetes cluster with NetworkPolicy-supporting CNI (Calico, Cilium, Antrea)
  • kubectl configured with admin access
  • Understanding of pod labels and selectors

Workflow

Step 1: Default Deny All Traffic
yaml
# default-deny-all.yaml - Apply to every namespace
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny-all
  namespace: production
spec:
  podSelector: {}  # Applies to all pods
  policyTypes:
    - Ingress
    - Egress
Step 2: Allow DNS Egress (Required for Service Discovery)
yaml
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-dns
  namespace: production
spec:
  podSelector: {}
  policyTypes:
    - Egress
  egress:
    - to:
        - namespaceSelector:
            matchLabels:
              kubernetes.io/metadata.name: kube-system
      ports:
        - protocol: UDP
          port: 53
        - protocol: TCP
          port: 53
Step 3: Application-Specific Policies
yaml
# Allow frontend to reach backend only
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: backend-allow-frontend
  namespace: production
spec:
  podSelector:
    matchLabels:
      app: backend
  policyTypes:
    - Ingress
  ingress:
    - from:
        - podSelector:
            matchLabels:
              app: frontend
      ports:
        - protocol: TCP
          port: 8080
---
# Allow backend to reach database only
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: database-allow-backend
  namespace: production
spec:
  podSelector:
    matchLabels:
      app: database
  policyTypes:
    - Ingress
  ingress:
    - from:
        - podSelector:
            matchLabels:
              app: backend
      ports:
        - protocol: TCP
          port: 5432
Step 4: Cross-Namespace Policies
yaml
# Allow monitoring namespace to scrape metrics
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: allow-monitoring-scrape
  namespace: production
spec:
  podSelector: {}
  policyTypes:
    - Ingress
  ingress:
    - from:
        - namespaceSelector:
            matchLabels:
              purpose: monitoring
      ports:
        - protocol: TCP
          port: 9090  # Prometheus metrics port
Step 5: Egress Restrictions
yaml
# Restrict egress to specific external services
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: restrict-egress
  namespace: production
spec:
  podSelector:
    matchLabels:
      app: backend
  policyTypes:
    - Egress
  egress:
    - to:
        - podSelector:
            matchLabels:
              app: database
      ports:
        - protocol: TCP
          port: 5432
    - to:  # Allow external API
        - ipBlock:
            cidr: 203.0.113.0/24
      ports:
        - protocol: TCP
          port: 443
    - to:  # DNS
        - namespaceSelector:
            matchLabels:
              kubernetes.io/metadata.name: kube-system
      ports:
        - protocol: UDP
          port: 53
Step 6: Block Cloud Metadata Access
yaml
# Prevent SSRF to cloud metadata service
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: block-metadata
  namespace: production
spec:
  podSelector: {}
  policyTypes:
    - Egress
  egress:
    - to:
        - ipBlock:
            cidr: 0.0.0.0/0
            except:
              - 169.254.169.254/32  # AWS/GCP metadata
              - 100.100.100.200/32  # Azure metadata

Validation Commands

bash
# Verify policies are applied
kubectl get networkpolicies -n production

# Test connectivity (should be blocked)
kubectl run test-pod --image=busybox --restart=Never -n production -- wget -qO- --timeout=2 http://database-service:5432
# Expected: timeout (blocked by policy)

# Test allowed traffic
kubectl run frontend-test --image=busybox --labels=app=frontend --restart=Never -n production -- wget -qO- --timeout=2 http://backend-service:8080
# Expected: connection succeeds

References

© mukul975, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 7 other files (scripts, references, assets) in skills/implementing-network-policies-for-kubernetes of mukul975/Anthropic-Cybersecurity-Skills.

  • SKILL.md
  • LICENSE
  • assets/template.md
  • references/api-reference.md
  • references/standards.md
  • references/workflows.md
  • scripts/agent.py
  • scripts/process.py

Open the folder on GitHubat commit 54a7988

Compare with similar skills

Implementing Network Policies For Kubernetes next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Implementing Network Policies For Kubernetes compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Implementing Network Policies For Kubernetes this skillmukul975/Anthropic-Cybersecurity-Skills34k—~1.5kAutomated safety check: PassApache-2.0
Kubeshark KFL2 Filter Referencekubeshark/kubeshark12k—~3.6kAutomated safety check: PassApache-2.0
Nginx To Higress Migrationhigress-group/higress9.5k—~3.9kAutomated safety check: PassApache-2.0
NGINX Ingress Controller Feature Checklistsnginx/kubernetes-ingress5.1k—~1.4kAutomated safety check: PassApache-2.0
NGINX Ingress Policy CRD Guidenginx/kubernetes-ingress5.1k—~2kAutomated safety check: PassApache-2.0
Aks Deployment Skilltimothywarner/chatgptclass143—~916Automated safety check: PassCustom licence

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Works with

Categories

Questions about Implementing Network Policies For Kubernetes

What does Implementing Network Policies For Kubernetes do?

Writes portable upstream Kubernetes NetworkPolicy YAML - default-deny-all, DNS egress, namespace and pod selector rules - that works on any conformant CNI such as Calico or Cilium. Implementing Network Policies For Kubernetes is an agent skill from mukul975/Anthropic-Cybersecurity-Skills. Writes portable upstream Kubernetes NetworkPolicy YAML - default-deny-all, DNS egress, namespace and pod selector rules - that works on any conformant CNI such as Calico or Cilium.

When should I use Implementing Network Policies For Kubernetes?

Implementing Network Policies For Kubernetes fits situations like: segmentation must stay CNI-portable; introducing a default-deny posture; restricting east-west traffic between pods and namespaces without depending on a vendor CRD; calico-specific resources - use implementing-kubernetes-network-policy-with-calico.

How do I install Implementing Network Policies For Kubernetes in Claude Code?

Run `npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill implementing-network-policies-for-kubernetes -a claude-code`. Or copy the skill folder (skills/implementing-network-policies-for-kubernetes in mukul975/Anthropic-Cybersecurity-Skills) into .claude/skills/implementing-network-policies-for-kubernetes in your project. Claude Code loads it when a task matches its description.

How do I install Implementing Network Policies For Kubernetes in Codex?

Run `npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill implementing-network-policies-for-kubernetes -a codex`. Or copy the skill folder (skills/implementing-network-policies-for-kubernetes in mukul975/Anthropic-Cybersecurity-Skills) into .agents/skills/implementing-network-policies-for-kubernetes in your project. Codex loads it when a task matches its description.

Can I use Implementing Network Policies For Kubernetes in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill implementing-network-policies-for-kubernetes -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/implementing-network-policies-for-kubernetes, .gemini/skills/implementing-network-policies-for-kubernetes, .github/skills/implementing-network-policies-for-kubernetes and .opencode/skills/implementing-network-policies-for-kubernetes in your project.

What does Implementing Network Policies For Kubernetes need to run?

Going by SKILL.md and its folder, Implementing Network Policies For Kubernetes needs Python for the scripts in its folder and the command-line tools its instructions call (kubectl). Our summary lists: Python 3.

Does Implementing Network Policies For Kubernetes access the network?

SKILL.md names 4 domains. As links in the text: kubernetes.io, docs.tigera.io, docs.cilium.io and editor.networkpolicy.io. This is read from the text; nothing was executed.

Is Implementing Network Policies For Kubernetes safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. The check reads SKILL.md only: the scripts in the folder are not scanned, so read them before running anything.

What licence does Implementing Network Policies For Kubernetes use?

Implementing Network Policies For Kubernetes is published under the Apache-2.0 licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Implementing Network Policies For Kubernetes use?

About 1.5k tokens (SKILL.md is roughly 6k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 748 tokens, read only when the agent opens those files.

What are the alternatives to Implementing Network Policies For Kubernetes?

Skills that share tags, products or a category with Implementing Network Policies For Kubernetes: Kubeshark KFL2 Filter Reference (kubeshark/kubeshark, 12k stars), Nginx To Higress Migration (higress-group/higress, 9.5k stars), NGINX Ingress Controller Feature Checklists (nginx/kubernetes-ingress, 5.1k stars) and NGINX Ingress Policy CRD Guide (nginx/kubernetes-ingress, 5.1k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Implementing Network Policies For Kubernetes?

mukul975 (a GitHub user) maintains it in mukul975/Anthropic-Cybersecurity-Skills, which has 34,116 GitHub stars. The repository holds 644 skills in this directory. The repository was last updated on August 31, 2026.

Source: mukul975/Anthropic-Cybersecurity-Skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.