Chapter 4 — Computers and operating systems

Lesson map

Lesson 04 published. Map, example, EX010.

flowchart TD
  N0["Learning outcomes"]
  N1["4.1 How computers run programs"]
  N2["4.2 Accounts and permissions"]
  N3["4.3 Updates"]
  N4["4.4 Malware basics"]
  N0 --> N1 --> N2 --> N3 --> N4
  N4 --> EX["Worked example"]
  EX --> Q["Exercise EX010"]

Logical drawing

flowchart LR
  N0["Learning outcomes"]
  N1["4.1 How computers run programs"]
  N2["4.2 Accounts and permissions"]
  N3["4.3 Updates"]
  N4["4.4 Malware basics"]
  N0 --> N1 --> N2 --> N3 --> N4 --> Q["EX010"]

[Learning outcomes]
    |
    v
[4.1 How computers run programs]
    |
    v
[4.2 Accounts and permissions]
    |
    v
[4.3 Updates]
    |
    v
[4.4 Malware basics]
    |
    v
[Worked example] --> [Exercise EX010]

Learning outcomes

You will (1) describe how computers run programs; (2) explain user accounts and permissions; (3) recognise why updates matter.

4.1 How computers run programs

Aisha learns that a computer runs programs under an operating system, which manages memory, files and devices. Each program runs as a process, and the operating system keeps processes apart so one cannot directly interfere with another. Ashfield's branch computers run a common desktop operating system, while its servers run another. Dr. Carrow explains that understanding these basics helps security staff see how attacks work and why certain controls are needed. Aisha installs a virtual machine on her laptop so she can explore an operating system safely without affecting her own files.

4.2 Accounts and permissions

Operating systems use accounts to decide who can do what. Standard accounts can run programs and use their own files; administrator accounts can install software and change settings. Aisha finds that some Ashfield branch staff use administrator accounts every day, because an old application once needed it. If one of these staff opens a malicious attachment, the malware gets administrator rights too. She recommends standard accounts for daily work. Ashfield's IT manager tests the old application with a standard account and finds it now works, so the daily administrator accounts can be removed.

4.3 Updates

Software contains flaws, and vendors publish updates to fix them. Attackers study updates to find what was fixed and then target systems not yet updated. Aisha checks a synthetic list of Ashfield computers and finds several weeks behind on updates because staff postpone restarts. She recommends automatic installation outside branch hours. Dr. Carrow notes that applying updates promptly is one of the most effective and least glamorous security practices. The IT manager agrees to schedule restarts at night, and Aisha suggests reporting the number of computers more than two weeks behind each month.

4.4 Malware basics

Malware is software designed to cause harm: stealing information, encrypting files for ransom or giving attackers remote control. It often arrives through email attachments, malicious websites or infected removable media. Aisha learns how antivirus and newer endpoint tools detect suspicious behaviour, and why they are not enough alone. She notes that standard accounts, prompt updates and careful email handling together reduce the chance malware succeeds. She writes a short journal entry comparing how each control would have stopped a ransomware infection described in a news article she read that week, which helps her remember why layers matter.

Worked example

Aisha learns process separation, finds daily administrator use in branches, recommends automatic updates and connects malware defences to accounts and updates.

Synthetic case. Computers are synthetic.

Errors and limits

Daily use of administrator accounts gives malware administrator rights.

Exercises

• EX010 — Admin cause. Why do some staff use administrator accounts?
  Show marking criteria

  Rubric: 3 = an old application once needed it;; 2 = partly correct;; 1 = vague;; 0 = none.
• EX011 — Update delay. Why are some computers behind on updates?
  Show marking criteria

  Rubric: 3 = staff postpone restarts;; 2 = partly correct;; 1 = vague;; 0 = none.
• EX012 — Malware routes. Name one way malware arrives.
  Show marking criteria

  Rubric: 3 = email attachments;; 2 = one;; 1 = vague;; 0 = none.