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Technologist · Chapter 13 · English

Chapter 13 — Network and communications security: risk scenarios

Open, free learning for anyone who wants to protect people and technology. No account is required to read this text or its worked answers.

Chapter 13 — Network and communications security: risk scenarios

Lesson map

Lesson 13 published. Map, example, EX037.

flowchart TD
  N0["Learning outcomes"]
  N1["13.1 Why scenarios"]
  N2["13.2 Scenario: curious student"]
  N3["13.3 Scenario: infected laptop"]
  N4["13.4 Scenario: misused supplier access"]
  N5["Synthesis"]
  N0 --> N1 --> N2 --> N3 --> N4 --> N5
  N5 --> EX["Worked example"]
  EX --> Q["Exercise EX037"]

Logical drawing

flowchart LR
  N0["Learning outcomes"]
  N1["13.1 Why scenarios"]
  N2["13.2 Scenario: curious student"]
  N3["13.3 Scenario: infected laptop"]
  N4["13.4 Scenario: misused supplier access"]
  N5["Synthesis"]
  N0 --> N1 --> N2 --> N3 --> N4 --> N5 --> Q["EX037"]

[Learning outcomes]
    |
    v
[13.1 Why scenarios]
    |
    v
[13.2 Scenario: curious student]
    |
    v
[13.3 Scenario: infected laptop]
    |
    v
[13.4 Scenario: misused supplier access]
    |
    v
[Synthesis]
    |
    v
[Worked example] --> [Exercise EX037]

Learning outcomes

You will (1) build realistic risk scenarios; (2) trace each through the network; (3) link scenarios to controls.

13.1 Why scenarios

Lists of threats can feel abstract. Scenarios tell a short story of how harm could happen, step by step, which helps people understand and helps designers check controls. Tomás writes four scenarios for the school, each based on common patterns rather than real events, and traces how each would unfold on the current network and on the proposed design. Scenarios also make good teaching material for staff, who can relate to a story more easily than to a technical diagram.

13.2 Scenario: curious student

A student finds the finance office printer in a list of network devices and prints to it repeatedly as a joke. Then the student finds a web page for the finance server and tries common passwords. On the current flat network, every step is possible. In the proposed design, students cannot reach the administration zone at all, so the printer and server are invisible, and denied attempts are logged. The scenario shows that separation removes the opportunity rather than relying on the student's restraint.

13.3 Scenario: infected laptop

A teacher's laptop is infected at home and brought into school. The malware searches the network for file shares and remote desktop services. On the current network, it finds the file server, whose remote desktop is open, and the finance server. In the proposed design, staff can reach teaching file shares but not finance; remote desktop is disabled; and denied connections generate logs that monitoring can notice. Tomás notes that the teaching file share remains reachable, so backups and host protection remain essential.

13.4 Scenario: misused supplier access

The heating company's old remote access tool is still connected directly to the main subnet. If its credentials were stolen, someone could connect from outside and reach any device. In the proposed design, supplier access goes through a controlled path with named accounts, reaches only the heating controller and is logged. This scenario persuades the head teacher to prioritise fixing supplier access, because it shows how a small, forgotten connection could expose the whole school to people outside it. The fix is scheduled first.

Worked example

Four scenarios are traced; three are blocked early in the proposed design and one is limited to teaching files.

Synthetic case. Scenarios are synthetic.

Errors and limits

Scenarios that assume attackers behave exactly as designers expect miss alternative paths.

Exercises

Synthesis

Scenarios turn abstract risks into stories that test controls and persuade decision makers.

Continue studying — chapter 13 of 30

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