← IGCSE Computer Science Paper 1

Trojan horse

Malware disguised as useful or harmless software. The user installs it willingly, then it secretly does harm, such as opening a back door or stealing data. It does not replicate itself.

Part of: IGCSE Computer Science 0478 — 5.3 Cyber Security — Module 9, ACARA Digital Technologies Years 7–8 — Networks and Cyber Threats — Module 17, ACARA Digital Technologies Years 9–10 — Cyber Security Threats and Vulnerabilities — Module 23, WA Computer Science ATAR Year 11 — Cyber Security — Module 35

Understanding Trojan horse in IGCSE Computer Science Paper 1

What it does: A Trojan does not copy itself or spread by itself. The user spreads it by downloading the disguised file. A virus attaches to files and replicates. The user runs the installer because the file looks useful or harmless, such as a free game. The hidden harmful action only runs after installation. Trojans often open a back door or steal data. They never help the user, even though they pretend to. Trojans hide in free or unofficial downloads. Trusted sources and reviews lower the risk but do not remove it completely. The name comes from the story of the wooden horse. It looked harmless, but soldiers were hiding inside. Trojans are not about speed or spreading.

Common mistakes: A Trojan horse is disguised as useful or harmless software, so looks_useful should be TRUE. Users only install it because it looks genuine. A Trojan horse does not replicate itself. This is a key difference from a virus or worm, so replicates should be FALSE.

Class: _____________________ · Name: _____________________ · Date: _________

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This module's key terms are also in a printable crossword (Modules 520–546) and word search (Modules 510–546).

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Learning

Duo

A student downloads a free game from an unknown website. While they play, it secretly steals their saved passwords. What type of malware is this?

FirewallTrojan horse

Matches

trojan.copies_itself = True

↓

A Trojan horse does not replicate itself. Saying it copies itself confuses it with a virus or worm.

Applying

Meanings

Term

Trojan horse

Meaning

Malware disguised as useful or harmless software. The user installs it willingly, then it secretly does harm, such as opening a back door or stealing data. It does not replicate itself.

Practice

// Trojan horse: fake free game

Testing

Gaps

A looks like a free app

Check Answer

Spots

1file ← "free_wallpaper.exe"

2looks_useful ← FALSE

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Quick Questions

1. A student downloads a free game from an unknown website. While they play, it secretly steals their saved passwords. What type of malware is this?

A. Firewall

B. Trojan horse ✓

A Trojan horse is disguised as useful or harmless software. The user installs it willingly, then it does hidden harm.

2. Which statement about how a Trojan horse gets onto a computer is correct?

A. It copies itself across the network on its own

B. The user installs it, thinking it is safe ✓

Trojans rely on the user choosing to install them. Copying itself across a network is what a worm does.

3. True or false: A Trojan horse replicates itself and spreads to other computers.

A. False ✓

B. True

A Trojan does not replicate itself. This is a key difference from a virus.

4. Which is a common aim of a Trojan horse?

A. Open a back door so a hacker can get in ✓

B. Make the computer run faster

Trojans often open a back door or steal data. They never help the user, even though they pretend to.

5. Which describes the main difference between a Trojan horse and a virus?

A. A Trojan pretends to be useful software but does not copy itself ✓

B. A Trojan copies itself into other files but a virus does not

A virus replicates by attaching to other files. A Trojan is disguised as useful software and does not replicate.

Match the Pairs

Trojan horse → Malware disguised as useful or harmless software that the user installs willingly, then secretly does harm

backdoor = True → A Trojan's aim: open a hidden way in so an attacker can access the computer or steal data later

A Trojan horse does not replicate itself, unlike a virus, so it relies on users choosing to install it → trojan.copies_itself = False

A Trojan is disguised as a free app or file that the user willingly installs → install("free_game.exe")

trojan.copies_itself = True → A Trojan horse does not replicate itself. Saying it copies itself confuses it with a virus or worm.

trojan.disguise = "none" → A Trojan horse must be disguised as useful or harmless software. With no disguise, the user would not install it willingly.

Key Term

Trojan horse

Malware disguised as useful or harmless software. The user installs it willingly, then it secretly does harm, such as opening a back door or stealing data. It does not replicate itself.

Fill in the Blanks

1. A Trojan horse looks like a free app

Hint: Type the name of the malware disguised as harmless, useful software.

2. A Trojan horse does not replicate itself

Hint: Type the verb for making copies of itself, which viruses and worms do but Trojans do not.

3. Trojan aim: open a back door or steal data

Hint: Type the two-word term for a hidden way into a computer that bypasses normal security.

4. A Trojan needs the user to install it

Hint: Type the verb for putting a program onto a computer, which the user does willingly because the Trojan is disguised.

5. virus.replicates = TRUE Trojan.replicates = FALSE

Hint: Type the Boolean value that shows a Trojan, unlike a virus, does not copy itself.

Spot the Error

Question 1

A file ← "free_wallpaper.exe"

B looks_useful ← FALSE

C user_installs ← TRUE

D hidden_action ← "open back door"

Line B — A Trojan horse is disguised as useful or harmless software, so looks_useful should be TRUE. Users only install it because it looks genuine.

Question 2

A app ← "free PDF converter"

B replicates ← TRUE

C hidden_aim ← "steal data"

Line B — A Trojan horse does not replicate itself. This is a key difference from a virus or worm, so replicates should be FALSE.

Question 3

A type ← "Trojan horse"

B installed_by ← "attacker"

C aim ← "open a back door"

Line B — The user installs a Trojan horse willingly, because they think it is useful. It should be installed_by ← "user".

Question 4

A malware ← "Worm"

B spreads_alone ← FALSE

C needs_user_to_install ← TRUE

Line A — The program describes a Trojan horse: it does not spread alone and needs the user to install it. A worm replicates itself, so the type should be "Trojan horse".

Question 5

A IF software = "Trojan" THEN

B disguised ← TRUE

C replicates ← FALSE

D aim ← "speed up the PC"

E ENDIF

Line D — A Trojan horse carries out a hidden harmful action, such as stealing data or opening a back door. It does not help the computer. It should be aim ← "steal data".

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