Chapter 2 — Accounts, devices and sharing

Chapter 2 — Accounts, devices and sharing

Lesson map

Lesson 02 published. Map, example, EX053.

flowchart TD
  N0["Learning outcomes"]
  N1["2.1 Own accounts"]
  N2["2.2 Second factor"]
  N3["2.3 Devices"]
  N4["Lab — Shared files open to anyone with the link, by"]
  N5["2.4 Over-shared files"]
  N6["2.5 Closing the gaps"]
  N7["Concepts — identity, possession, and exposure"]
  N0 --> N1 --> N2 --> N3 --> N4 --> N5 --> N6 --> N7
  N7 --> EX["Worked example"]
  EX --> Q["Exercise EX053"]

Logical drawing

flowchart LR
  N0["Learning outcomes"]
  N1["2.1 Own accounts"]
  N2["2.2 Second factor"]
  N3["2.3 Devices"]
  N4["Lab — Shared files open to anyone with the link, by"]
  N5["2.4 Over-shared files"]
  N6["2.5 Closing the gaps"]
  N7["Concepts — identity, possession, and exposure"]
  N0 --> N1 --> N2 --> N3 --> N4 --> N5 --> N6 --> N7 --> Q["EX053"]

[Learning outcomes]
    |
    v
[2.1 Own accounts]
    |
    v
[2.2 Second factor]
    |
    v
[2.3 Devices]
    |
    v
[Lab — Shared files open to anyone with the link, by]
    |
    v
[2.4 Over-shared files]
    |
    v
[2.5 Closing the gaps]
    |
    v
[Concepts — identity, possession, and exposure]
    |
    v
[Worked example] --> [Exercise EX053]

Learning outcomes

You will (1) give each person their own account with a second factor; (2) secure the clinic's devices; (3) find and close over-shared files with a short script.

2.1 Own accounts

Sofia finds that reception staff share one login to the practice management system, written on a note under the keyboard. Mr. Nowak explains that shared logins hide who did what, and the note means anyone at the desk could sign in. The system supports personal accounts with quick switching between users, so Sofia sets up one account per person and removes the note. Reception staff worry about delays, so she times the switch during a busy morning and shows that it takes a few seconds. Dr. Moss approves the change after seeing the timing.

2.2 Second factor

Mr. Nowak explains that most account takeovers start with a stolen or guessed password, and that a second factor, such as an app on a phone, stops most of them. Sofia turns on a second factor for email and the practice system, starting with Dr. Moss and the office team, who handle payments, then everyone else over two weeks. Two nurses do not want work apps on their own phones, so the clinic buys two small security keys for them. Sofia records each person's method in the change log so lost devices can be handled quickly.

2.3 Devices

Sofia checks the nine computers and two tablets with the technician. Three computers have updates switched off because an old label printer stopped working after an update last year. The technician installs a newer printer driver and switches updates back on. All devices now lock after five minutes, and staff accounts can no longer install software. The tablets used in consulting rooms get a passcode and remote wipe. Mr. Nowak notes that switching updates off to solve one problem is common, and that the fix is to solve the underlying problem instead of leaving devices exposed.

Lab — Shared files open to anyone with the link, by folder, in a synthetic file store

"""Find synthetic shared files open to anyone with the link, by folder (stdlib only)."""
import random
from collections import Counter
random.seed(2)
files = []
for folder, n, p in [("clients", 140, 0.04), ("finance", 60, 0.05), ("marketing", 80, 0.30), ("rotas", 20, 0.5)]:
    for i in range(n):
        files.append((folder, random.random() < p))
total = Counter(f for f, _ in files)
open_ = Counter(f for f, o in files if o)
for f in total:
    print(f"{f}: {open_[f]} of {total[f]} open to anyone with the link")
print(f"all files: {sum(open_.values())} of {len(files)}")

Run with python3 lab_sharing.py. Verified output:

clients: 8 of 140 open to anyone with the link
finance: 4 of 60 open to anyone with the link
marketing: 25 of 80 open to anyone with the link
rotas: 10 of 20 open to anyone with the link
all files: 47 of 300

2.4 Over-shared files

With Dr. Moss's permission, the technician exports a list of shared files and whether each is open to anyone with the link. Sofia runs the script on a synthetic copy with the same folder structure. It finds 47 of 300 files open to anyone with the link. Most are marketing photos, 25 of 80, and staff rotas, 10 of 20. But 8 of 140 files in the client folder and 4 of 60 in the finance folder are also open. Those twelve matter most, because anyone who obtains a link could read client or bank information.

2.5 Closing the gaps

Sofia changes the twelve client and finance files to clinic-only sharing first. She then asks staff why rotas were shared openly and learns that part-time staff check them from home on personal phones. She moves the rota to the practice system, where staff can see it after signing in. Marketing photos can stay public because they are already posted online. Sofia asks the technician to set the default for new shares to clinic-only, and adds a monthly reminder to rerun the check. Mr. Nowak praises her for fixing the reason behind the rota sharing, not just the setting.

Worked example

Sofia replaces a shared reception login, turns on second factors with security keys for two nurses, re-enables updates on three computers and finds 47 of 300 synthetic files open to anyone, including 12 client and finance files.

Synthetic case. Accounts, devices and files are synthetic.

Errors and limits

Switching off updates to fix a printer leaves devices exposed long after the printer is forgotten.

Concepts — identity, possession, and exposure

Three different controls are easy to mix up because all three are "turned on" in the same week.

The rota shows the third limit. Closing a link without replacing the work makes part-time staff invent a new workaround. Sofia moved the rota into the practice system, behind sign-in, because the home check was a real task.

Data — the synthetic share count, ranked by harm

The verified script, seed 2, printed these counts. Rank follows harm, not the size of the number.

Twelve is 8 plus 4. Those twelve outrank the 25 marketing files. A monthly rerun catches a new share that used the old default.

Decision flow — a person, a device, or a link

flowchart TD
  A["A request this week"] --> B{"Will two people write notes under one name?"}
  B -->|Yes| C["Create a personal account. Remove the shared note. Time the switch"]
  B -->|No| D{"Is the only barrier a password someone could reuse?"}
  D -->|Yes| E{"Can this person use a work app on their own phone?"}
  E -->|Yes| F["Turn on the app as the second factor"]
  E -->|No| G["Issue a security key and record it in the change log"]
  D -->|No| H{"Is a client or finance file open to anyone with the link?"}
  H -->|Yes| I["Set clinic-only before any other folder"]
  H -->|No| J{"Do staff need that file from outside?"}
  J -->|Yes| K["Put the task behind sign-in. Do not leave the open link"]
  J -->|No| L["If it is already public marketing, leave it and record why"]

Updates sit beside this flow. Three computers had updates off because a label printer broke. The repair is a newer driver, then updates on. Leaving updates off keeps every other flaw on those machines after the printer is forgotten.

Worked example — a locum who starts on Monday

A locum vet covers Monday and is told to use the reception login "only for this week". Sofia refuses. Notes written that day would be attributed to the shared desk, which is the defect in section 2.1. She creates a personal account before the first patient, turns on a second factor, and asks Dr. Moss to approve the account in the change log. She does not wait to time the switch: the reception timing already showed a few seconds, and a week of shared notes would outlast the locum. When the locum leaves, the same log says which account to disable.

Synthetic case. The locum and the one-week instruction are invented.

Apply

• EX053 — Locum account. What must exist before the locum's first patient, and which record says when to disable it? Rubric: 3 = a personal account with a second factor, approved in the change log; the same log names the account to disable when the locum leaves;; 2 = the personal account only;; 1 = vague;; 0 = none.
• EX054 — Order the open files. Using the verified counts, which 12 files are closed first, which folder is moved behind sign-in, and which open files may stay? Rubric: 3 = 8 client and 4 finance first; rotas move behind sign-in; marketing may stay because it is already public;; 2 = the twelve and one other action;; 1 = a count without the action;; 0 = none.

Exercises

• EX014 — Shared login. What did reception use to sign in? Rubric: 3 = one shared login on a note;; 2 = partly correct;; 1 = partial;; 0 = none.
• EX015 — Switch time. How long does switching users take? Rubric: 3 = a few seconds;; 2 = partly correct;; 1 = vague;; 0 = none.
• EX016 — First MFA group. Who got a second factor first? Rubric: 3 = Dr. Moss and the office team;; 2 = partly correct;; 1 = partial;; 0 = none.
• EX017 — Security keys. Why were security keys bought? Rubric: 3 = two nurses declined apps on personal phones;; 2 = partly correct;; 1 = vague;; 0 = none.
• EX018 — Updates off. Why were updates off on three computers? Rubric: 3 = an old label printer broke after an update;; 2 = partly correct;; 1 = vague;; 0 = none.
• EX019 — Update fix. How was the printer problem fixed? Rubric: 3 = a newer printer driver;; 2 = partly correct;; 1 = other;; 0 = none.
• EX020 — Tablet controls. What did the consulting room tablets get? Rubric: 3 = passcode and remote wipe;; 2 = both;; 1 = one;; 0 = none.
• EX021 — Open total. How many files were open to anyone with the link? Rubric: 3 = 47 of 300;; 2 = partly correct;; 1 = wrong;; 0 = none.
• EX022 — Marketing count. How many marketing files were open? Rubric: 3 = 25 of 80;; 2 = partly correct;; 1 = wrong;; 0 = none.
• EX023 — Sensitive open. How many client and finance files were open? Rubric: 3 = 12 (8 client, 4 finance);; 2 = partly correct;; 1 = partial;; 0 = none.
• EX024 — Rota cause. Why were rotas shared openly? Rubric: 3 = part-time staff checked them from home;; 2 = partly correct;; 1 = vague;; 0 = none.
• EX025 — Rota fix. Where did the rota move? Rubric: 3 = into the practice system;; 2 = partly correct;; 1 = other;; 0 = none.
• EX026 — Default setting. What default did the technician set? Rubric: 3 = clinic-only sharing for new shares;; 2 = partly correct;; 1 = other;; 0 = none.

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