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AQA GCSE Computer Science

Network and cyber security — AQA GCSE Computer Science revision

Free revision notes, key terms, common exam traps and 5 practice questions with answers. About 7 minutes to read.

Malware and social threats

  • Malware is malicious software designed to damage, disrupt or gain unauthorised access to systems.
  • Viruses attach to files and replicate when the file is run, often corrupting or deleting data; worms self-replicate across networks without needing a host file.
  • Trojans disguise themselves as legitimate software to trick users into installing them, often opening a backdoor for attackers.
  • Spyware secretly monitors user activity (e.g. keystrokes) and sends data to an attacker; ransomware encrypts a victim's files and demands payment to unlock them.
  • Phishing uses fake emails or websites that impersonate trusted organisations to trick users into revealing personal information.

Technical attacks

  • A brute force attack tries many password combinations systematically until the correct one is found.
  • A Denial of Service (DoS) attack floods a server with fake requests, overwhelming it so legitimate users cannot access the service; a DDoS uses many devices at once.
  • Data interception involves intercepting data as it travels across a network, often using packet sniffing on unsecured connections.
  • SQL injection involves entering malicious SQL code into an input box on a website to access, change or delete data in a database it should not be able to reach.

Key terms

Malware
Malicious software designed to damage or gain unauthorised access to a system.
Virus
Malware that attaches to files and replicates when the file runs.
Worm
Self-replicating malware that spreads across networks without a host file.
Trojan
Malware disguised as legitimate software.
Ransomware
Malware that encrypts files and demands payment to restore access.
Phishing
Fraudulent messages impersonating trusted sources to steal information.

Common exam traps

  • Confusing a virus (needs a host file) with a worm (self-replicating, no host needed).
  • Thinking phishing is a technical attack — it's a social engineering technique using deception.
  • Believing a firewall alone stops all malware — it filters traffic but doesn't remove malware already on a device.

Practice questions with answers

  1. 1. What is malware?

    • • Software that improves performance
    • • Malicious software designed to harm or exploit systems
    • • A type of firewall
    • • A network protocol

    Answer: Malicious software designed to harm or exploit systems

    Malware is any software created to cause damage or gain unauthorised access.

  2. 2. Which malware type requires a host file to spread?

    • • Worm
    • • Virus
    • • Ransomware
    • • Spyware

    Answer: Virus

    A virus attaches to a file and spreads when that file is executed.

  3. 3. How does a worm differ from a virus?

    Answer: Worms self-replicate across networks without needing a host file

    Worms spread independently, unlike viruses which need a host file to run.

  4. 4. Which malware disguises itself as legitimate software?

    • • Trojan
    • • Worm
    • • Ransomware
    • • Spyware

    Answer: Trojan

    A Trojan tricks users into installing it by appearing to be genuine software.

  5. 5. What does ransomware do?

    • • Deletes files immediately
    • • Monitors keystrokes
    • • Encrypts files and demands payment
    • • Floods a server with traffic

    Answer: Encrypts files and demands payment

    Ransomware locks a victim's data with encryption and demands a ransom for the key.

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