Security, privacy and integrity: threats, firewalls, encryption and digital signatures

Last time

Before we start: last time, in The operating system and utility software, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.

Three words that sound alike

A school keeps names, addresses and exam results on its computers. Security means keeping that data safe from people who should not see it. Privacy means respecting the rights of the people the data is about. Integrity means the data stays accurate. Each has its own threats, and its own defences.

Three terms

Data security is protecting data from unauthorised access, damage or loss. Data privacy is the right of a person to control who collects, holds and uses their personal data. Data integrity is keeping data accurate, complete and consistent, so it has not been changed by mistake or on purpose.

Malware

A virus attaches itself to a file or program, and spreads when that is run or copied. It can corrupt or delete data. A worm spreads on its own across a network. A trojan pretends to be useful software. Spyware secretly records what you do. Ransomware locks data until a payment is made.

Tricks on the user

Phishing is an email or message that looks genuine and tricks the user into giving away details, usually by clicking a link. Pharming installs code on a computer or server which redirects the user, from the real website address to a fake site, even when the right address is typed.

A past-paper example

Cambridge 9618, October November 2025, Paper 11, question 8 part a. Viruses and pharming are examples of malware. Explain what is meant by a virus and pharming. Two marks. A virus is malicious code that attaches itself to files or programs, copies itself when they run, and can damage or delete data. Pharming is malware that redirects a user from a genuine website to a fake one, to collect their personal details.