Identifying and preventing vulnerabilities – GCSE Computer Science exam questions with mark scheme

1Grade 6–74 marks

A school network stores students' records and teachers' files.

(a) Explain how user access levels help to keep the data secure. [2]

(b) Explain how a firewall protects the school network. [2]

(a) Different users are given different permissions / rights (e.g. read-only, read/write, no access) e.g. students cannot access teachers' files(1)
(a) This limits who can view / change / delete sensitive data, reducing the damage from mistakes, insiders or a stolen student login(1)
(b) A firewall monitors / checks incoming and outgoing traffic (packets) against a set of rules(1)
(b) It blocks / allows traffic based on these rules (e.g. blocks unauthorised access / certain ports / suspicious IP addresses)(1)
Answer: (a) Users only get the permissions they need, so sensitive data can't be seen or changed by others (b) Checks traffic against rules and blocks unauthorised traffic
Examiner tip: A firewall does not remove viruses – that is anti-malware. Describe it as filtering traffic using rules.

2Grade 8–96 marks

An online bank has suffered brute-force attacks on customer accounts and a denial of service attack on its website.

Explain how the bank could protect itself against both of these threats. [6]

Brute-force (max 3), any three from, each method with why it works: strong passwords (long, mix of character types) so there are too many combinations to try in a reasonable time; lock the account / add a delay after a set number of failed attempts so thousands of guesses cannot be made; two-factor / multi-factor authentication so a guessed password alone does not give access; CAPTCHA to stop automated guessing by bots; monitor login attempts and block IP addresses with many failures. Lock-out after failed attempts and blocking an IP after failed attempts count as one point. A method named with no reason does not earn the mark(1)
Brute-force: second, different method with reason(1)
Brute-force: third, different method with reason(1)
DoS (max 3), any three from, each method with why it works: firewall that detects and blocks unusual / excessive traffic (e.g. many requests from one IP address); monitor traffic to identify the source and block those IP addresses (counts as the same point as a firewall blocking those IP addresses); rate-limit requests per IP address; extra servers / bandwidth / cloud load-balancing so the site can cope with the extra traffic; allow penetration / stress testing so weaknesses can be found and fixed before an attack. A method named with no reason does not earn the mark(1)
DoS: second, different method with reason(1)
DoS: third, different method with reason(1)
Answer: Strong passwords, lock-out after failed attempts and 2FA/CAPTCHA against brute force; firewall rules, monitoring/blocking IP addresses and extra capacity against DoS
Examiner tip: Answer both threats – a full answer about passwords with nothing on DoS caps you at 3 marks. Explain why each method works.

Still losing marks on this topic?

Book a free introductory session and we'll find exactly which step is costing you.

Book a free intro