Harbor Plant / 02 / PRACTICE GUIDE

Zones, conduits and trust boundaries

Review a fictional plant diagram using an actual local JSON model. Distinguish what DMZ, control and safety boundaries establish and what remains unproven.

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Original AI-assisted SecNet educational content; examples are fictional. Not a source organization publication or endorsement. Sources checked: 2026-10-21.

Local plant review desk

Use synthetic models only. Input is neither transmitted nor saved to an account. Include no real architecture, secrets or personal data.

Synthetic plant JSON

{
  "version": 1,
  "caseId": "harbor-plant",
  "zones": [
    {
      "id": "enterprise",
      "name": "Enterprise planning",
      "kind": "enterprise"
    },
    {
      "id": "dmz",
      "name": "Industrial DMZ",
      "kind": "dmz"
    },
    {
      "id": "operations",
      "name": "Operations",
      "kind": "operations"
    },
    {
      "id": "control",
      "name": "Control cell",
      "kind": "control"
    },
    {
      "id": "safety",
      "name": "Separate safety zone",
      "kind": "safety"
    }
  ],
  "assets": [
    {
      "id": "planner",
      "name": "Planning workstation",
      "zone": "enterprise",
      "owner": "Business systems"
    },
    {
      "id": "jump",
      "name": "Maintenance jump point",
      "zone": "dmz",
      "owner": "Access owner"
    },
    {
      "id": "engineer",
      "name": "Engineering station",
      "zone": "operations",
      "owner": "Site engineering"
    },
    {
      "id": "controller",
      "name": "Filling controller",
      "zone": "control",
      "owner": "Process owner"
    },
    {
      "id": "safety-unit",
      "name": "Safety boundary placeholder",
      "zone": "safety",
      "owner": "Safety authority"
    }
  ],
  "conduits": [
    {
      "id": "c-01",
      "from": "planner",
      "to": "jump",
      "enabled": true,
      "purpose": "Declared support request",
      "reviewRef": "review-01"
    },
    {
      "id": "c-02",
      "from": "jump",
      "to": "engineer",
      "enabled": true,
      "purpose": "Declared maintenance path",
      "reviewRef": "review-02"
    },
    {
      "id": "c-03",
      "from": "engineer",
      "to": "controller",
      "enabled": true,
      "purpose": "Declared engineering dependency",
      "reviewRef": "review-03"
    }
  ]
}

Enabled arrows are directed. The shortest path and shortest path excluding DMZ assets are sought; not all paths, actual packets, ports, protocols, NAT or firewall rule order. A supplied review reference verifies no document. No SL/SIL assignment or safety approval is performed.

EVIDENCE REVIEW DESK

Move from observations to decisions.

Code here is a local policy model with no target connection. Passing model cases are not security approval or device tests.

Drawn boundary / Incomplete decision

Inspect an incomplete decision based on record existence or another positive signal. Consider denial cases alongside permitted use.

s => s.diagramExists === true

A diagram establishes neither risk rationale nor implemented controls. Without flow ownership and authorized safety-boundary review, colored boxes remain architectural assumptions.

Choices and outputs last only on this open page; they do not update account progress, career status, points or certificates.

01 / EXPLANATION

A layered drawing is not an access policy

Harbor contains a planning workstation, industrial DMZ jump host, operations station, controller and separate safety zone. Layered drawings help communication; no single topology is mandatory for every site. Define zones through shared security requirements and risk context. Devices drawn on the same layer need not share trust. Separately assess how network and identity controls implement each boundary. Reducing process and safety dependencies to IP subnets can conceal functional relationships and common failure risks. A tidy diagram is only one input to an engineering and security review.

02 / EXPLANATION

Conduit purpose and direction

A conduit expresses communication needs across zones in a controlled design. Record source/destination, purpose, initiating direction, required service, owner and review reference. An open port does not establish business need or trusted identity. Each arrow in the Harbor JSON exercise is a declared directed connection; response traffic is not inferred. The tool evaluates no real protocol, port, firewall order, route, NAT or state tracking. This deliberate scope lets learners examine a logical path without mistaking a drawing result for a device configuration assessment.

03 / EXPLANATION

Separate security levels from safety

Security level SL in the IEC 62443 context and functional-safety SIL are different concepts and cannot be converted into one another. Writing a level on a zone does not show its target requirements are satisfied. Record the target, scope and assessment evidence separately. Authorized safety engineering evaluates safety-system independence and the effect of connections. This original exercise reproduces no standard text or licensed requirements list and provides no conformity assessment, SL/SIL assignment or accredited-training claim. Real standards-based work also requires the relevant licensed edition.

04 / EXPLANATION

Interpret the local path review

Compare the two synthetic files: a declared DMZ route and an alternative with a direct shortcut. Across enabled arrows, the tool seeks the shortest path and the shortest path excluding DMZ assets per enterprise/external source and control target. It separately lists arrows lacking review references and safety-boundary connections. A reference does not verify a document. Finding no path is not proof of isolation; missing inventory and undeclared connections remain outside the model. The output is a set of questions and evidence IDs for an owner, not an instruction to disconnect a real process.

Build the evidence yourself.

Blank workpapers are not completed tests. Fill them in your authorized environment without secrets or real personal data.

Process scope and review authorityMarkdown · EN Boundary and evidence review planMarkdown · EN Observation, dependency and gap recordMarkdown · EN Authorized review and handoverMarkdown · EN

Full guide with code, outputs and reasoning ↓

Primary references

Explanations are authored by SecNet. References support method and platform context; verify current editions and organizational policy for real use.