What is Malware?
Malware (malicious software) is any software deliberately designed to cause harm to a computer, network, or user. The word is short for "malicious software", and it is an umbrella term covering many different types of harmful programs.
Malware can steal your personal data, damage your files, use your computer for criminal activity, or hold your data for ransom — often without you even knowing it is there.
Types of Malware
| Type | What It Does |
|---|---|
| Virus | Attaches itself to legitimate files and spreads when those files are shared. Can corrupt or delete data. |
| Worm | Spreads automatically across networks without user action. Can overload systems and carry other malware. |
| Trojan | Disguises itself as useful software. Once installed, it creates a back door for attackers. |
| Ransomware | Encrypts your files and demands payment for the decryption key. |
| Spyware | Secretly monitors your activity, stealing passwords and personal information. |
| Adware | Displays unwanted adverts, often slowing the computer down. |
| Rootkit | Hides deep in the OS to give attackers persistent, hidden access. |
Ransomware attacks have hit hospitals, schools, and businesses worldwide, demanding thousands of pounds in cryptocurrency. Always keep backups of important files — if ransomware encrypts your data, a recent backup means you can restore without paying.
How Malware Spreads
Malware needs a way to get onto your device in the first place. Common delivery methods include:
- Email attachments: Opening a malicious attachment runs the malware
- Malicious downloads: Software downloaded from unofficial sources
- Phishing links: Clicking a link in a fake email takes you to a site that installs malware
- Infected USB drives: Plugging in an unknown USB drive
- Unpatched software: Security vulnerabilities in out-of-date software
How to Stay Protected
Good security comes from multiple layers of protection working together — no single measure is 100% effective on its own.
Key defences include:
- Antivirus software: Scans files and running processes for known malware signatures, and monitors for suspicious behaviour
- Keeping software up to date: Software updates often patch security vulnerabilities that malware exploits
- Using a firewall: Monitors network traffic and blocks suspicious connections
- Being cautious online: Avoid clicking suspicious links, downloading from unofficial sources, or opening unexpected email attachments
- Regular backups: Even if malware strikes, a recent backup means you can restore your data
What Antivirus Software Does
Antivirus programs protect your computer in two main ways:
- Signature detection: Compares files against a database of known malware patterns
- Heuristic/behaviour detection: Watches for suspicious activity (like a program suddenly trying to encrypt thousands of files)
Practice Problems
Describe the difference between a virus and a worm. Which is more dangerous in terms of spreading across a network and why?
Show answer
A student receives an email from an unknown sender with an attachment called 'free_games.exe'. Describe two security risks and explain what they should do.