Chapter 1 — Advanced security decision-making
Lesson map
Lesson 01 published. Map, example, EX001.
flowchart TD
N0["Learning outcomes"]
N1["1.1 Framing the decision"]
N2["1.2 Expected loss and burden"]
N3["Lab — Expected loss reduction and staff hours for tw"]
N4["1.3 Documenting rationale"]
N5["Synthesis"]
N0 --> N1 --> N2 --> N3 --> N4 --> N5
N5 --> EX["Worked example"]
EX --> Q["Exercise EX001"]
Logical drawing
flowchart LR
N0["Learning outcomes"]
N1["1.1 Framing the decision"]
N2["1.2 Expected loss and burden"]
N3["Lab — Expected loss reduction and staff hours for tw"]
N4["1.3 Documenting rationale"]
N5["Synthesis"]
N0 --> N1 --> N2 --> N3 --> N4 --> N5 --> Q["EX001"]
[Learning outcomes]
|
v
[1.1 Framing the decision]
|
v
[1.2 Expected loss and burden]
|
v
[Lab — Expected loss reduction and staff hours for tw]
|
v
[1.3 Documenting rationale]
|
v
[Synthesis]
|
v
[Worked example] --> [Exercise EX001]
Learning outcomes
You will (1) frame human-centred security decisions under uncertainty; (2) use expected loss alongside staff burden; (3) document decision rationale for leaders.
1.1 Framing the decision
Daniel Osei, a security manager studying part-time at the fictional Westbrook School of Professional Studies, faces a decision at the fictional Calloway Insurance, a firm of 900 staff. The board wants to know whether to buy an expanded simulation service or invest in faster reporting and verification controls. His course leader, Dr Ingrid Holm, asks him to frame the decision explicitly: the options, the outcomes that matter, the uncertainties and the people affected. A clear frame prevents the choice from being made on vendor enthusiasm or habit alone.
1.2 Expected loss and burden
Daniel estimates expected annual loss from payment fraud and credential theft under each option, using ranges rather than single numbers because evidence is uncertain. He adds staff burden, estimated in hours per year, because Herley (2009) showed that security advice imposes real costs on users that organisations often ignore. The lab compares options by expected loss reduction and by staff hours, showing that the verification option reduces more loss while costing staff fewer hours, though the ranges overlap enough to require judgement.
Lab — Expected loss reduction and staff hours for two options
# Expected loss reduction (thousands) and staff hours for two options (synthetic, triangular estimates).
opts = {"verification and reporting": ((180, 300, 450), 1800), "expanded simulations": ((60, 130, 230), 4500)}
for name, ((lo, mode, hi), hrs) in opts.items():
mean = (lo + mode + hi) / 3
print(f"{name}: expected loss reduction {mean:.0f}k (range {lo}-{hi}k), staff hours {hrs}")
Run with python3 lab_decide.py. Verified output:
verification and reporting: expected loss reduction 310k (range 180-450k), staff hours 1800
expanded simulations: expected loss reduction 140k (range 60-230k), staff hours 4500
1.3 Documenting rationale
Daniel writes a two-page decision note for the board stating the options, estimates, assumptions and his recommendation for the verification and reporting option. He records what would change his mind, such as evidence that simulation results predict real fraud losses. The note uses plain language and shows ranges. Documenting the rationale lets the board challenge the reasoning, and it creates a record that future reviewers can compare with actual outcomes, which supports learning across decisions rather than only within one. The board reads it before the meeting.
Worked example
Daniel frames a programme choice at Calloway Insurance, compares expected loss and staff hours and documents a recommendation with conditions for change.
Synthetic case. Calloway and all figures are synthetic; Herley (2009) is real.
Errors and limits
Loss estimates are uncertain. Hours estimates may omit hidden effort.
Exercises
- EX001 — Decision frame. What elements make up Daniel's decision frame? Rubric: 3 = options, outcomes, uncertainties and people affected;; 2 = frame;; 1 = vague;; 0 = none.
- EX002 — Herley cost. Why include staff hours following Herley (2009)? Rubric: 3 = security advice imposes real user costs;; 2 = burden;; 1 = vague;; 0 = none.
- EX003 — Lab comparison. How did the two options compare on loss reduction and hours? Rubric: 3 = verification 310k and 1,800 h; simulations 140k and 4,500 h;; 2 = verification better;; 1 = vague;; 0 = none.
- EX004 — Mind-changer. What evidence would change Daniel's mind? Rubric: 3 = simulation results predicting real fraud losses;; 2 = prediction;; 1 = vague;; 0 = none.
- EX005 — Note purpose. Why document the rationale? Rubric: 3 = so it can be challenged and compared with outcomes later;; 2 = record;; 1 = vague;; 0 = none.
Synthesis
Advanced decisions frame options, weigh loss and burden and record rationale openly.