← IGCSE Computer Science Paper 1

OS function: providing system security

An OS function that protects the computer and its data from unauthorised access and attack using logins, access rights, updates and security tools.

Part of: IGCSE Computer Science 0478 — 4.1 Types of Software and Interrupts — Module 28, ACARA Digital Technologies Years 9–10 — Networked Systems and Access Control — Module 113

Understanding OS function: providing system security in IGCSE Computer Science Paper 1

What it does: Built-in or supported security tools such as a firewall and antivirus guard against attack, which is a key part of the OS security function. Applying security updates patches vulnerabilities in the OS, so attackers cannot use them to gain access. Logins with passwords stop unauthorised users getting into the computer. Fetching instructions is the CPU's job, not OS security. Access rights limit what each user can do with a file, so private data is protected from people who should not see or change it. Strong passwords are hard to guess. Common words like 'password' are easy for attackers to guess, which weakens the OS login protection.

Common mistakes: The login check uses <> (not equal), so access is granted when the password is wrong. It should be IF password = savedPass THEN so only the correct password logs the user in. A guest should only get the lowest access rights needed. Giving FULL_ACCESS lets them write and delete files. It should be rights ← READ_ONLY.

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This module's key terms are also in a printable crossword (Modules 373–389) and word search (Modules 356–389).

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Learning
Duo
Which is an example of the OS providing system security?
Asking users to log in with a username and passwordLetting the CPU fetch the next instruction
Matches
Password: 1234 (shared by all users)
↓
A weak password that is shared by everyone gives poor security. Each user needs their own strong password so the OS can identify them and block unauthorised access.
Applying
Meanings
Term
system security
Meaning
An OS function that protects the computer and its data from unauthorised access and attack using logins, access rights, updates and security tools.
Practice
INPUT password
Testing
Gaps
IF password storedPassword THEN
Check Answer
Spots
1INPUT username, password
2IF password <> savedPass THEN

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Quick Questions

1. Which is an example of the OS providing system security?
A. Asking users to log in with a username and password ✓
B. Letting the CPU fetch the next instruction
Logins with passwords stop unauthorised users getting into the computer. Fetching instructions is the CPU's job, not OS security.
2. How does the OS use access rights to protect files?
A. It decides which users can read, write or execute each file ✓
B. It gives every user full access to every file
Access rights limit what each user can do with a file, so private data is protected from people who should not see or change it.
3. Why does an OS install security updates?
A. To fix weaknesses that attackers could use ✓
B. To make the screen resolution higher
Security updates (patches) fix vulnerabilities so malware and hackers cannot exploit them.
4. Which statement about security tools and the OS is correct?
A. An OS can never work with a firewall or antivirus software
B. The OS can include or support a firewall and antivirus software ✓
Many operating systems have a built-in firewall and antivirus, or let you install them, to block attacks and detect malware.
5. Which password is the better choice for protecting a user account?
A. The word password
B. A long mix of letters, numbers and symbols ✓
Strong passwords are hard to guess. Common words like 'password' are easy for attackers to guess, which weakens the OS login protection.

Match the Pairs

Username + Password → A login check that makes the OS confirm who the user is before it allows access to the computer
Access rights: read only → The user can open and view a file but cannot change or delete it
The OS protects the computer from malware by running security tools such as a firewall and antivirus → Firewall: ON | Antivirus: ON
The OS fixes weaknesses that hackers could exploit by installing security updates → Install update: security patch
Password: 1234 (shared by all users) → A weak password that is shared by everyone gives poor security. Each user needs their own strong password so the OS can identify them and block unauthorised access.
Ignore security updates to save time → Ignoring security updates leaves known weaknesses unpatched, so attackers can exploit them. Security updates should be applied as soon as possible.

Key Term

system security
An OS function that protects the computer and its data from unauthorised access and attack using logins, access rights, updates and security tools.

Fill in the Blanks

1. INPUT password IF password = storedPassword THEN OUTPUT "Login accepted"
Hint: Type the comparison operator that checks whether the entered password matches the stored one.
2. IF accessRight = "read" THEN OUTPUT "File opened as read-only" ENDIF
Hint: Type the keyword that displays a message to the user when read access is granted.
3. IF updateAvailable = TRUE THEN installUpdate() ENDIF
Hint: Type the Boolean value that means a security update is waiting, so the OS should install it.
4. threat ← scanFile(download) IF threat = TRUE THEN blockFile(download)
Hint: Type the function name that makes the antivirus check a download for malware.
5. IF attempts >= 3 THEN lockAccount() ENDIF
Hint: Type the operator meaning greater than or equal to, so the account locks after too many failed logins.

Spot the Error

Question 1
A INPUT username, password
B IF password <> savedPass THEN
C OUTPUT "Access granted"
D ELSE OUTPUT "Access denied"
Line B — The login check uses <> (not equal), so access is granted when the password is wrong. It should be IF password = savedPass THEN so only the correct password logs the user in.
Question 2
A user ← "guest"
B rights ← FULL_ACCESS
C IF action = "write" THEN
D OUTPUT "Not allowed"
Line B — A guest should only get the lowest access rights needed. Giving FULL_ACCESS lets them write and delete files. It should be rights ← READ_ONLY.
Question 3
A attempts ← 0
B REPEAT
C attempts ← attempts - 1
D INPUT password
E UNTIL correct OR attempts = 3
Line C — The counter must go up by 1 each try so the account is locked after 3 failed attempts. Subtracting means it never reaches 3, so guessing is unlimited. It should be attempts ← attempts + 1.
Question 4
A CHECK for updates
B IF update_found THEN
C DOWNLOAD patch
D DELETE patch
E ENDIF
Line D — A security update only protects the computer once it is installed. Deleting the patch leaves the weakness open to attack. It should be INSTALL patch.
Question 5
A FOR EACH packet IN traffic
B IF source IN blocklist THEN
C ALLOW packet
D ELSE ALLOW packet
E NEXT packet
Line C — The firewall must stop traffic from blocklisted sources. Allowing it lets the unwanted traffic in. It should be BLOCK packet.

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