Chapter 2 — Networks and protocols

Lesson map

Lesson 02 published. Map, example, EX005.

flowchart TD
  N0["Learning outcomes"]
  N1["2.1 The practice network"]
  N2["2.2 Protocols in use"]
  N3["2.3 Weak settings"]
  N4["Synthesis"]
  N0 --> N1 --> N2 --> N3 --> N4
  N4 --> EX["Worked example"]
  EX --> Q["Exercise EX005"]

Logical drawing

flowchart LR
  N0["Learning outcomes"]
  N1["2.1 The practice network"]
  N2["2.2 Protocols in use"]
  N3["2.3 Weak settings"]
  N4["Synthesis"]
  N0 --> N1 --> N2 --> N3 --> N4 --> Q["EX005"]

[Learning outcomes]
    |
    v
[2.1 The practice network]
    |
    v
[2.2 Protocols in use]
    |
    v
[2.3 Weak settings]
    |
    v
[Synthesis]
    |
    v
[Worked example] --> [Exercise EX005]

Learning outcomes

You will (1) describe a practice network; (2) explain key protocols in use; (3) find network settings that weaken security.

2.1 The practice network

Nadia sketches a typical Linden practice. A router connects to the internet and provides wireless for staff and a separate guest network for patients. A switch connects reception PCs, surgery PCs, the imaging server, X-ray sensors and printers. Card terminals connect through the wired network to the payment provider. Each practice has a site-to-site VPN to head office for backups. Drawing the network helps her see that surgery devices and reception PCs share one flat network, so any infected PC can reach the imaging server directly.

2.2 Protocols in use

Daniel asks Nadia to identify protocols. Browsers use HTTPS to reach the practice management system. The imaging server shares files using SMB, a Windows file sharing protocol. Card terminals use encrypted connections defined by the payment provider. DHCP hands out addresses, and DNS resolves names. Backups travel through the VPN using IPsec. Knowing the protocols lets her ask the right questions, such as which SMB version the imaging server uses, because old versions have well-known weaknesses exploited by ransomware. She records each protocol and its port on the network sketch.

2.3 Weak settings

Nadia checks settings with Grace's permission. The imaging server still allows SMB version 1, the router's administration page is reachable from the guest wireless, and printers have default passwords. Grace disables SMB version 1 after confirming the imaging software no longer needs it, restricts router administration to the staff network and changes printer passwords. Nadia records each change. She notes that the flat network remains the biggest issue and needs a planned redesign rather than a quick fix, which she will return to later.

Worked example

Nadia sketches a practice network, lists the protocols in use and finds three weak settings that Grace fixes, noting the flat network for redesign.

Synthetic case. Network details are synthetic.

Errors and limits

Old software may need old protocols. Router changes can disrupt card terminals if done carelessly.

Exercises

• EX005 — Flat network risk. Why is the flat practice network a risk?
  Show marking criteria

  Rubric: 3 = any infected PC can reach the imaging server;; 2 = spread;; 1 = vague;; 0 = none.
• EX006 — SMB question. Why ask which SMB version the imaging server uses?
  Show marking criteria

  Rubric: 3 = old versions have weaknesses exploited by ransomware;; 2 = ransomware;; 1 = vague;; 0 = none.
• EX007 — Router fix. How was router administration restricted?
  Show marking criteria

  Rubric: 3 = to the staff network, not guest wireless;; 2 = staff only;; 1 = vague;; 0 = none.
• EX008 — Larger issue. What issue needs a planned redesign?
  Show marking criteria

  Rubric: 3 = the flat network;; 2 = flat network, hedged with another option;; 1 = printers;; 0 = none.

Synthesis

Understanding a network and its protocols reveals weak settings that can be fixed and design issues that need planning.

Continue studying — chapter 02 of 18

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