Understand what malware is and the main forms, including viruses, worms, trojans, spyware and ransomware, and the harm each can cause.

What this dot point is asking

AQA wants you to explain what malware is and describe the main forms (viruses, worms, trojans, spyware and ransomware) and the harm each can cause.

What malware is

Viruses, worms and trojans

The key contrast the exam tests is the method of spread. A virus is passive: it sits in a host file and needs the file to be run. A worm is active: it copies itself across a network on its own, which is why worms can spread far faster than viruses. A trojan spreads neither way by itself; it relies on tricking the user into installing it, which links to social engineering.

Spyware and ransomware

The harm caused

Malware can delete or steal data, slow or crash systems, capture passwords and banking details, lock users out of their files, and spread to other machines, causing serious financial cost and disruption. Different types cause different harm, so a good answer matches the harm to the type (spyware steals secretly, ransomware locks and demands payment).

How malware gets onto a system

Knowing how malware arrives helps explain how to defend against it. Common routes are: opening an infected email attachment or a malicious download (often a trojan disguised as useful software), clicking a link to a malicious website, plugging in an infected USB stick, or a worm exploiting an unpatched weakness across a network. Most of these routes rely on either a software vulnerability or a tricked user, which is why the main defences are anti-malware software to detect and remove malicious code, keeping software patched to close the weaknesses worms exploit, and user training so people do not open suspicious attachments or downloads.

Defending against malware

No single measure is enough, so defences are layered: anti-malware software scans files and blocks known threats; a firewall limits the network connections a worm could use to spread; regular, offline backups let data be restored after a ransomware attack without paying; software updates remove the vulnerabilities malware exploits; and user awareness reduces the trickery that delivers trojans and spyware. Matching each defence to the way a particular type of malware spreads is the key to a strong exam answer, rather than just listing "use antivirus".

Try this

Q1. State what malware is. [1 mark]

• Cue. Malicious software written to damage or gain unauthorised access to a computer system.

Q2. Describe how ransomware harms a victim. [2 marks]

• Cue. It encrypts the victim's files and demands a payment in exchange for the key to unlock them.