Chapter 7 — Networks and protocols

Lesson map

Lesson 07 published. Map, example, EX019.

flowchart TD
  N0["Learning outcomes"]
  N1["7.1 The network"]
  N2["7.2 Data leaving"]
  N3["7.3 Network risk"]
  N4["Synthesis"]
  N0 --> N1 --> N2 --> N3 --> N4
  N4 --> EX["Worked example"]
  EX --> Q["Exercise EX019"]

Logical drawing

flowchart LR
  N0["Learning outcomes"]
  N1["7.1 The network"]
  N2["7.2 Data leaving"]
  N3["7.3 Network risk"]
  N4["Synthesis"]
  N0 --> N1 --> N2 --> N3 --> N4 --> Q["EX019"]

[Learning outcomes]
    |
    v
[7.1 The network]
    |
    v
[7.2 Data leaving]
    |
    v
[7.3 Network risk]
    |
    v
[Synthesis]
    |
    v
[Worked example] --> [Exercise EX019]

Learning outcomes

You will (1) describe Elmfield's network and its external connections; (2) identify where data leave the organisation; (3) relate network design to risk.

7.1 The network

Elmfield's office network connects laptops and the file server, with internet access through a firewall. Most services now run in the cloud, reached over the internet. Repairs tablets connect through mobile networks. Sofia learns that the old idea of a trusted internal network no longer fits, because staff and data are spread across many places. Governance must therefore focus on identity, devices and data protection wherever they are, not only on the office firewall. Repairs tablets on mobile networks, for instance, never pass through the office firewall at all.

7.2 Data leaving

Sofia traces where tenant data leave Elmfield: email to contractors, the housing system supplier's servers, the payment provider and the payroll bureau. Each flow needs a reason, a contract and protection in transit. She finds that repairs contractors receive full tenant records when they need only a name, address and phone number. She recommends sending only the necessary fields, applying the principle of data minimisation, which reduces harm if a contractor's systems are compromised. Sending only name, address and phone number would also shrink what Elmfield must report if a contractor is breached.

7.3 Network risk

Sofia lists network risks: an exposed remote desktop service on the file server, a guest Wi-Fi network sharing the office network and no logging at the firewall. She ranks them by potential harm and ease of fixing. Closing the remote desktop exposure ranks first because attackers routinely scan for it. She learns that small fixes can remove large risks and that a network review is a quick way for a small organisation to find serious problems. The guest Wi-Fi and firewall logging issues follow, as both are cheap to fix but less likely to be exploited first.

Worked example

Sofia maps Elmfield's network and data flows, applies minimisation to contractor data and ranks three network risks.

Synthetic case. Elmfield's network is synthetic.

Errors and limits

Data flows change. Rankings depend on judgement.

Exercises

• EX019 — Trusted network. Why does the trusted internal network idea no longer fit?
  Show marking criteria

  Rubric: 3 = staff and data are spread across many places;; 2 = cloud and mobile;; 1 = vague;; 0 = none.
• EX020 — Minimisation fix. What should contractors receive instead of full records?
  Show marking criteria

  Rubric: 3 = name, address and phone only;; 2 = minimum fields;; 1 = full records;; 0 = none.
• EX021 — Top network risk. Which network risk ranked first?
  Show marking criteria

  Rubric: 3 = exposed remote desktop on the file server;; 2 = RDP;; 1 = vague;; 0 = none.

Synthesis

Network and data-flow maps show where protection and minimisation matter most.

Continue studying — chapter 07 of 40

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