AS · Practice questions · Threats to computer systems and how to protect them

Match the measure.

Six original Cambridge-style questions on threats from networks and the internet and the measures that reduce them, with mark-scheme style solutions.

Original questions All questions on this page are original work, written in the Cambridge AS & A Level style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

Threat, harm, measure.

Name and describe: say what the threat is and what harm it does.
Match: pick the measure that actually stops that threat.
Explain how: a firewall filters traffic by rules; anti-virus compares with signatures; encryption makes data unintelligible.
Context: a stand-alone PC and a network need different measures; use the scenario in the question.

Explain

[4 marks]

Explain the difference between phishing and pharming.

Phishing: the user receives an email or message that appears to come from a genuine organisation. ✓
Phishing: the user clicks a link in the message and is taken to a fake website where they enter personal details. ✓
Pharming: malicious code on the computer, or a corrupted DNS server, redirects the user to a fake website. ✓
Pharming: this happens even when the user types the genuine URL, so the user does not need to click anything. ✓

Recall

[2 marks]

Describe what is meant by spyware.

Malware installed without the user's knowledge that monitors the user's activity, for example recording key presses. ✓
The recorded data (such as passwords) is sent to a third party. ✓

Explain

[3 marks]

Describe how anti-virus software protects a computer.

It scans files and memory (on access or on a schedule). ✓
It compares code with a database of known virus signatures / looks for suspicious behaviour (heuristics). ✓
Infected files are quarantined or deleted, and the user is alerted; the signature database is updated regularly. ✓

Apply

[4 marks]

A small business has four stand-alone PCs that it is about to connect to a LAN with internet access. Identify two new threats the connection introduces, and for each describe a measure that reduces the risk.

Hackers can now attempt to access the PCs from outside the business. ✓
Measure: a firewall between the LAN and the internet filters traffic against rules and blocks unauthorised traffic (or strong passwords / access rights). ✓
Malware (viruses or spyware) can arrive by email or download and spread between the PCs over the LAN. ✓
Measure: up-to-date anti-virus / anti-spyware software on every PC, scanning files and downloads. ✓

Analysis

[3 marks]

A manager says: "We have a firewall, so our data is completely secure." Give three reasons why this is not true.

A firewall does not stop malware brought in by users, for example on a USB drive or in an email attachment. ✓
It does not stop an authorised user misusing their access or deleting data by mistake (access rights and backups are needed). ✓
It does not stop phishing / a user giving away a password, or protect data if a device is stolen (encryption needed). ✓

Apply

[3 marks]

Describe three rules a company could set for passwords to reduce the risk of hacking.

A minimum length, for example at least 12 characters. ✓
A mix of upper case, lower case, digits and symbols, and no dictionary words or personal details. ✓
The account is locked after a set number of failed attempts / passwords are changed regularly and not reused. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.