Describe methods that can be used to restrict the risks posed by threats

6.1 Data Security

1. Terminology & Core Concepts

• Security: protecting information from unauthorised access, modification, loss or destruction.
• Privacy: the right of individuals to control *who* may view or use their personal data.
• Integrity: ensuring data are accurate, complete and unaltered (e.g., by checksums, hashes, parity bits).
• Distinction: privacy concerns *who* can see data, security concerns *how* data are protected, and integrity concerns *whether* the data remain correct.

2. Threats to Computer & Data Security

Students should be able to name and briefly describe each threat. The wording follows the Cambridge syllabus.

• Malware – viruses, worms, spyware, ransomware that corrupt or steal data.
• Phishing & social engineering – deceptive messages that trick users into revealing credentials.
• Hacking – unauthorised exploitation of software or network vulnerabilities.
• Insider threat – accidental or deliberate misuse by authorised users (e.g., copying confidential files to a USB stick).
• Denial‑of‑Service (DoS) – overwhelming a service so it becomes unavailable.
• Physical theft or damage – loss or destruction of laptops, servers, or storage media.

3. Security Measures for Stand‑Alone PCs and Networks

• Stand‑alone PC (e.g., a school laptop):
  • User accounts & strong passwords.
  • File‑system permissions (read/write/execute).
  • Local firewall (Windows Defender Firewall, iptables).
  • Full‑disk encryption (BitLocker, FileVault).
  • Anti‑malware software with real‑time scanning.
• Networked environment (e.g., school LAN):
  • Network firewalls and router ACLs.
  • Intrusion detection/prevention systems (IDS/IPS).
  • Secure Wi‑Fi (WPA2‑Enterprise, captive portal).
  • Regular patching of servers, switches and client OSes.
  • Centralised authentication (Active Directory, LDAP).

4. Risk‑Management Process (Identify → Analyse → Evaluate → Treat → Review)

1. Identify assets – data, hardware, software, services.
2. Analyse threats & vulnerabilities – what could go wrong and why?
3. Evaluate likelihood & impact – use a risk matrix (see section 9).
4. Treat risk – select and implement appropriate controls.
5. Review – monitor effectiveness and update controls as needed.

Classroom example: “Risk – unauthorised use of USB drives → Treat – disable USB ports on all workstations and enforce a policy that only approved devices may be connected.”

5. Categories of Controls

5.1 Physical Controls

• Locked doors, security guards, CCTV – lab example: keep the computer room door locked when not in use.
• Environmental protection – fire suppression, temperature & humidity monitoring.
• Hardware protection – cable locks, locked server racks, tamper‑evident seals, BIOS/UEFI passwords.
• Media disposal – shredding paper, degaussing or physically destroying magnetic storage.
• Hardware‑level security – Trusted Platform Module (TPM), secure boot, firmware signing.

5.2 Technical (Logical) Controls

5.3 Administrative Controls

• Security policies – acceptable‑use, data‑classification, password standards, incident‑response.
• Procedures – step‑by‑step instructions for user provisioning, backup, media disposal, and a documented incident‑response plan (detect, contain, eradicate, recover, post‑mortem).
• Training & awareness – regular sessions on phishing, password hygiene, safe handling of removable media.
• Auditing & logging – maintain system logs, review them for unusual activity, conduct periodic audits.
• Legal & ethical context – recognise relevant legislation (e.g., GDPR, Data Protection Act) and the ethical responsibilities of a computer scientist.

6. Data Integrity Techniques (6.2 Data Integrity)

• Verification – confirming that data received are exactly what was sent (e.g., comparing a downloaded file’s checksum with the publisher’s checksum).
• Validation – checking that input conforms to expected rules before processing (e.g., range check: 0 ≤ age ≤ 120; format check: email contains “@”).
• Checksums & Cryptographic Hashes – MD5, SHA‑1/256 used to detect accidental corruption or intentional tampering.
• Parity bits & Error‑detecting codes – simple methods for detecting single‑bit errors in storage or transmission.

7. Encryption & Digital Certificates

• Symmetric encryption – same key encrypts and decrypts (e.g., AES). Fast, suitable for large files or disk encryption.
• Asymmetric encryption – public key encrypts, private key decrypts (e.g., RSA). Used for key exchange and digital signatures.

SSL/TLS Handshake (simplified) – the process that creates a secure channel for web traffic:

Client Hello  →  Server Hello
               →  Server Certificate (X.509)
               →  Server Key Exchange (if needed)
               →  Server Hello Done
Client Certificate (optional)
Client Key Exchange (pre‑master secret encrypted with server’s public key)
ChangeCipherSpec
Finished
               ←  ChangeCipherSpec
               ←  Finished

After the handshake both sides possess the same session key, which is used for symmetric encryption of the data stream.

8. Risk‑Reduction Techniques (Combining Controls)

1. Least Privilege – give users only the access they need for their role.
2. Defence in Depth – layered security (Physical → Network → Host → Application) so that failure of one layer does not expose the whole system.
3. Segmentation & Zoning – separate networks (DMZ, internal LAN, guest Wi‑Fi) to limit lateral movement.
4. Secure Development Lifecycle (SDLC) – integrate security activities (code review, static analysis, penetration testing) into each development stage.
5. Incident‑Response Plan – predefined steps for detection, containment, eradication, recovery and post‑incident review.

9. Example Risk‑Assessment Matrix

10. Summary of Key Methods to Restrict Risks

• Apply strong encryption (symmetric for bulk data, asymmetric for key exchange and digital signatures).
• Enforce robust authentication (strong passwords, MFA, biometrics) and authorisation (RBAC, ACLs).
• Maintain up‑to‑date anti‑malware, firewalls, IDS/IPS and systematic patch management.
• Secure the physical environment and protect hardware from environmental hazards.
• Implement regular backups following the 3‑2‑1 rule and test restores periodically.
• Maintain clear security policies, documented procedures (including an incident‑response plan), and conduct regular training and awareness sessions.
• Adopt a layered (defence‑in‑depth) approach that combines physical, technical and administrative controls.
• Use data‑integrity checks (checksums, hashes, parity) and digital certificates to verify authenticity.
• Validate input and verify output to satisfy the syllabus requirement for data integrity techniques.