Chapter 12 — Operating systems

Lesson map

Lesson 12 published. Map, example, EX034.

flowchart TD
  N0["Learning outcomes"]
  N1["12.1 Prompts and habits"]
  N2["12.2 Removing prompts"]
  N3["12.3 Accepted least privilege"]
  N4["Synthesis"]
  N0 --> N1 --> N2 --> N3 --> N4
  N4 --> EX["Worked example"]
  EX --> Q["Exercise EX034"]

Logical drawing

flowchart LR
  N0["Learning outcomes"]
  N1["12.1 Prompts and habits"]
  N2["12.2 Removing prompts"]
  N3["12.3 Accepted least privilege"]
  N4["Synthesis"]
  N0 --> N1 --> N2 --> N3 --> N4 --> Q["EX034"]

[Learning outcomes]
    |
    v
[12.1 Prompts and habits]
    |
    v
[12.2 Removing prompts]
    |
    v
[12.3 Accepted least privilege]
    |
    v
[Synthesis]
    |
    v
[Worked example] --> [Exercise EX034]

Learning outcomes

You will (1) examine how operating system prompts affect behaviour; (2) reduce unnecessary security prompts; (3) design least-privilege defaults that people accept.

12.1 Prompts and habits

Aiko counts security prompts that Greyford's office laptops show in a week: update reminders, permission requests, certificate warnings and administrator prompts. Staff see dozens. Most are routine, so people click through them by habit. When a rare dangerous prompt appears, the habit carries over. Herley (2009) argued that asking users to evaluate frequent warnings that are mostly harmless is a poor bargain for them. Reducing routine prompts makes the important ones stand out. She records the weekly count per laptop as a baseline before changing anything, so the effect of later changes can be measured.

12.2 Removing prompts

Aiko works with the IT team to remove prompts. Updates install automatically outside working hours. Common software is pre-approved, so staff need not request administrator rights to install it. Certificate warnings for internal systems are eliminated by fixing the internal certificates. After the changes, weekly prompts per laptop fall sharply. Staff notice fewer interruptions, and the IT team receives fewer help desk calls about prompts. She measures the change by counting prompts on ten laptops for a week before and after, and shares the results with staff along with a short explanation of which prompts still matter and why they should read them.

12.3 Accepted least privilege

Removing local administrator rights often meets resistance. Aiko designs an approach staff accept: a self-service catalogue for approved software, a fast request route for anything else with a response within one working hour, and temporary rights for engineers who need them for specific tasks. Least privilege succeeds when its costs to staff are low. She measures acceptance by counting requests and complaints for a month after the change. She also asks staff representatives to review the approach before launch, and they suggest adding commonly used engineering tools to the catalogue, which reduces requests in the first month.

Worked example

Aiko counts weekly prompts, removes routine ones through automation and pre-approval, and designs least privilege with a catalogue and fast requests.

Synthetic case. Counts and processes are synthetic; Herley (2009) is real.

Errors and limits

Automatic updates can break software. Temporary rights need expiry checks.

Exercises

• EX034 — Habit risk. Why are frequent routine prompts dangerous?
  Show marking criteria

  Rubric: 3 = habitual clicking carries over to rare dangerous prompts;; 2 = habit;; 1 = vague;; 0 = none.
• EX035 — Certificate fix. How were internal certificate warnings removed?
  Show marking criteria

  Rubric: 3 = by fixing internal certificates;; 2 = fix certs;; 1 = ignore;; 0 = none.
• EX036 — Acceptance design. What makes least privilege acceptable to staff?
  Show marking criteria

  Rubric: 3 = self-service catalogue, one-hour requests and temporary rights;; 2 = low cost;; 1 = vague;; 0 = none.

Synthesis

Fewer, meaningful prompts and low-cost least privilege make secure operating systems usable.

Continue studying — chapter 12 of 50

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