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Network Security

FoundationHigherAQA

Revise Network Security for GCSE Computer Science with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers. Networks are protected using authentication, encryption, firewalls and MAC address filtering.

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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA specification. Every worksheet comes with a full mark scheme.

Foundation

WorksheetFoundation · PDFMark SchemeFoundation · PDF

Higher

WorksheetHigher · PDFMark SchemeHigher · PDF

Topic overview

Network security protects data and systems from unauthorised access, and several measures work together rather than any one being sufficient.

Authentication confirms who a user is, using passwords or two-factor authentication. Encryption scrambles data so intercepted traffic is unreadable. A firewall examines traffic entering and leaving the network and blocks anything not permitted by its rules.

MAC address filtering allows only listed devices to connect. Access levels restrict what each user can see and do, so a compromised account cannot reach everything. Physical security matters too — a server room left unlocked defeats every software measure protecting it.

Revision notes

Authentication and encryption

Authentication confirms a user's identity, using passwords or two-factor authentication.

Encryption scrambles data so that intercepted traffic is meaningless without the key. Encryption does not prevent interception; it makes intercepted data useless.

Firewalls and filtering

A firewall examines traffic entering and leaving the network, blocking anything its rules do not permit.

MAC address filtering allows only specifically listed devices to connect, which is useful on a wireless network where anyone in range could otherwise attempt to join.

Access levels and physical security

Access levels restrict what each user can see and do.

A compromised account then reaches only part of the system rather than everything. Physical security matters too — an unlocked server room defeats every software measure protecting it.

Key points

  • Authentication confirms who a user is.
  • Encryption makes intercepted data unreadable.
  • A firewall blocks traffic its rules do not permit.
  • MAC filtering allows only listed devices.
  • Access levels limit what each user can do.
  • Physical security is also required.

Worked examples

Example 1

Explain how a firewall protects a network. [2 marks]

Working

It examines all traffic entering and leaving the networkstate what it does
and blocks anything that its rules do not permit, preventing unauthorised accessexplain the protection

Example 2

Explain why access levels improve security. [2 marks]

Working

Each user can only see and do what their role requiresstate what they do
so if an account is compromised, the attacker reaches only part of the system rather than everythingexplain the benefit

Example 3

Explain why physical security matters alongside software measures. [2 marks]

Working

An attacker with physical access to a server can bypass software protections entirelystate the risk
so an unlocked server room defeats firewalls, passwords and encryption alikeexplain the consequence

Common mistakes

  • Relying on a single measure.

    Security comes from several measures working together.

  • Saying encryption prevents interception.

    It makes intercepted data unreadable rather than preventing capture.

  • Forgetting physical security.

    It is specifically examinable and often overlooked.

  • Confusing authentication with authorisation.

    Authentication confirms identity; access levels determine permissions.

Exam tips

  • Name several measures working together.
  • Explain each measure's mechanism.
  • Include physical security in your answer.
  • Say encryption makes data unreadable, not uninterceptable.

Key terms

Firewall
Software examining and blocking network traffic.
MAC address filtering
Allowing only listed devices to connect.
Access level
A restriction on what a user may see and do.
Physical security
Protecting hardware from physical access.

Related topics

Written and reviewed against the current AQA specification. Spotted an error? Let us know.