IB Computer Science HL · Year 2 · Lesson 42

Network security + A2 Paper 1 synthesis

Network security is a layered risk-management problem: identify threats, understand vulnerabilities and select proportionate countermeasures. Networks exist to move data and share resources reliably across connected devices and infrastructures.

Paper 150 minutesA2.4.1 · A2.4.2 · A2.4.3 · A2.4.4 · A2.1.1 · A2.1.2 · A2.1.3…
Use Next or the arrow keys.
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Today’s targets

What you need to be able to do

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  • DiscussThe effectiveness of firewalls at protecting a network
  • DescribeCommon network vulnerabilities
  • DescribeCommon network countermeasures
  • DescribeThe process of encryption and digital certificates
  • RetrieveReconnect today’s new material to previously taught content from this topic.
A2.4.1A2.4.2A2.4.3A2.4.4A2.1.1A2.1.2A2.1.3A2.1.4A2.1.5A2.2.1A2.2.2A2.2.3A2.2.4A2.3.1A2.3.2A2.3.3A2.3.4
Paper 1 lensMatch the depth of every response to the command term. Previously learned content can move quickly, but retrieval must still be accurate.
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Retrieve

Rapid Recall Deck

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Say the answer aloud before flipping. Mark secure knowledge quickly and spend time on the gaps.

  • What does a firewall do?: It inspects and filters incoming and outgoing network traffic using rules such as allow/deny lists and other policy conditions.
  • Why can a firewall not provide complete network security by itself?: It cannot stop every threat, especially attacks using allowed traffic, compromised insiders, social engineering, unknown vulnerabilities, or poorly configured rules.
  • What are common network vulnerabilities?: DDoS, insecure protocols, malware, MitM, phishing, SQL injection, XSS, unpatched software, weak authentication, and zero-day exploits.
  • What is the difference between an IDS and an IPS?: An IDS detects and alerts on suspicious activity; an IPS can actively block or prevent detected malicious traffic.
  • Which countermeasures reduce authentication and communication risk?: Examples include MFA, strong password policies, encrypted protocols, TLS certificates, VPNs, software updates, filtering, and security testing/training.
  • What is the difference between symmetric and asymmetric cryptography?: Symmetric cryptography uses the same secret key for encryption and decryption; asymmetric cryptography uses a mathematically related public/private key pair.
  • What is the role of a digital certificate?: It binds an identity to a public key through a trusted certificate process, helping establish authenticated secure network connections.
  • Why is encryption key management important?: Keys must be generated, stored, distributed, rotated, and protected securely because exposed or mismanaged keys can defeat the encryption.
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A2.4.1 + A2.4.2 · Learn

Core knowledge and application

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A2.4.1Discuss

The effectiveness of firewalls at protecting a network

Network security is a layered risk-management problem: identify threats, understand vulnerabilities and select proportionate countermeasures.

Exam moveGive a balanced, evidence-based treatment of different sides before concluding.
Required detail 1The function of firewalls in inspecting and filtering incoming and outgoing traffic based on whitelists, blacklists and rules
Required detail 2The strengths and limitations of firewalls
Required detail 3Role of NAT to enhance network security

Explain it without notes

Discuss: The effectiveness of firewalls at protecting a network in the context of a school network responding to phishing, malware and interception risks.

  • The function of firewalls in inspecting and filtering incoming and outgoing traffic based on whitelists, blacklists and rules
  • The strengths and limitations of firewalls
  • Role of NAT to enhance network security
A2.4.2Describe

Common network vulnerabilities

Network security is a layered risk-management problem: identify threats, understand vulnerabilities and select proportionate countermeasures.

Exam moveGive a detailed, accurate account of what happens or what something is like.
Required detail 1Distributed denial of service (DDoS), insecure network protocols, malware, man-in-the-middle (MitM) attacks, phishing attacks, SQL injection, cross-site scripting (XSS), unpatched software, weak authentication, zero-day exploits

Explain it without notes

Describe: Common network vulnerabilities in the context of a school network responding to phishing, malware and interception risks.

  • Distributed denial of service (DDoS), insecure network protocols, malware, man-in-the-middle (MitM) attacks, phishing attacks, SQL injection, cross-site scripting (XSS), unpatched software, weak authentication, zero-day exploits
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A2.4.3 + A2.4.4 · Learn

Core knowledge and application

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A2.4.3Describe

Common network countermeasures

Network security is a layered risk-management problem: identify threats, understand vulnerabilities and select proportionate countermeasures.

Exam moveGive a detailed, accurate account of what happens or what something is like.
Required detail 1Content security policies, complex password policies, DDoS mitigation tools, email filtering solutions, encrypted protocols, input validation (filtering, whitelisting), intrusion detection systems (IDS), intrusion prevention systems (IPS), multifactor authentication (MFA), secure socket layer (SSL) certificate, transport layer security (TLS) certificate, update software, VPNs
Required detail 2The importance of regular security testing and employee training
Required detail 3Wireless security measures may include media access controllers (MAC), whitelists and blacklists

Explain it without notes

Describe: Common network countermeasures in the context of a school network responding to phishing, malware and interception risks.

  • Content security policies, complex password policies, DDoS mitigation tools, email filtering solutions, encrypted protocols, input validation (filtering, whitelisting), intrusion detection systems (IDS), intrusion prevention systems (IPS), multifactor authentication (MFA), secure socket layer (SSL) certificate, transport layer security (TLS) certificate, update software, VPNs
  • The importance of regular security testing and employee training
  • Wireless security measures may include media access controllers (MAC), whitelists and blacklists
A2.4.4Describe

The process of encryption and digital certificates

Network security is a layered risk-management problem: identify threats, understand vulnerabilities and select proportionate countermeasures.

Exam moveGive a detailed, accurate account of what happens or what something is like.
Required detail 1Compare symmetric and asymmetric cryptography
Required detail 2Role of digital certificates in establishing secure network connections
Required detail 3Use of public and private keys in asymmetric cryptography
Required detail 4The significance of encryption key management

Explain it without notes

Describe: The process of encryption and digital certificates in the context of a school network responding to phishing, malware and interception risks.

  • Compare symmetric and asymmetric cryptography
  • Role of digital certificates in establishing secure network connections
  • Use of public and private keys in asymmetric cryptography
  • The significance of encryption key management
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Apply

Transfer to a new scenario

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ScenarioA school network responding to phishing, malware and interception risks needs a design or technical decision related to today’s topic. Explain what matters and why.
  • The function of firewalls in inspecting and filtering incoming and outgoing traffic based on whitelists, blacklists and rules
  • The strengths and limitations of firewalls
  • Distributed denial of service (DDoS), insecure network protocols, malware, man-in-the-middle (MitM) attacks, phishing attacks, SQL injection, cross-site scripting (XSS), unpatched software, weak authentication, zero-day exploits
  • Content security policies, complex password policies, DDoS mitigation tools, email filtering solutions, encrypted protocols, input validation (filtering, whitelisting), intrusion detection systems (IDS), intrusion prevention systems (IPS), multifactor authentication (MFA), secure socket layer (SSL) certificate, transport layer security (TLS) certificate, update software, VPNs
  • The importance of regular security testing and employee training
  • Compare symmetric and asymmetric cryptography
  • Role of digital certificates in establishing secure network connections
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Exam lens

Paper 1 practice

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Build the response before checking notesUse precise terminology and match the required depth.
  1. Discuss: The effectiveness of firewalls at protecting a network in the context of a school network responding to phishing, malware and interception risks.
  2. Describe: Common network vulnerabilities in the context of a school network responding to phishing, malware and interception risks.
  3. Describe: Common network countermeasures in the context of a school network responding to phishing, malware and interception risks.
Self-checkAnswer the exact command term. For explain, include mechanism/reason; for compare, pair criteria; for discuss/evaluate/justify, build supported reasoning and a conclusion.
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2027 Case Study

Generative AI research checkpoint

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Build a reusable evidence bank for Paper 1 Section B. Keep claims technical, specific and supported.

Research checkpoint

Research deployment infrastructure: what networking/security/resource constraints matter when serving generative models?

Challenge focus: Explain how iterative denoising creates images and evaluate the computational demands of the process.

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Homework

Finish the learning cycle

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IA — main task

Complete Criterion E and final IA quality checks. Evaluate the product against success criteria and propose specific, feasible improvements.

Syllabus — short

Complete a short Paper 1 retrieval task; keep the IA as the main workload.

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End of Lesson 42.