1.5 Malicious Software

What is Malware?

Malware (malicious software) is any program designed to harm, exploit, or disable systems, devices, or networks without the user's consent. Malware can steal data, spy on users, disrupt operations, or grant attackers unauthorized access. It spreads through email attachments, infected downloads, removable media, or network vulnerabilities.

Common Malware Types

A virus attaches to files and needs a host program to spread. A worm self-replicates across networks without human action. A trojan disguises itself as legitimate software. Ransomware encrypts data and demands payment. Spyware secretly monitors user activity, while adware floods users with unwanted ads. A rootkit hides deep in the system to maintain stealthy, privileged access.

Botnets and Keyloggers

A botnet is a network of infected devices ('zombies') controlled remotely by an attacker to launch large-scale attacks like DDoS. A keylogger records keystrokes to steal passwords and sensitive information. Understanding these threats helps security professionals design defenses like antivirus software, network monitoring, and user training.

Key terms

Malware

Malicious software designed to harm, exploit, or disable systems without user consent.

Virus vs. Worm

A virus needs a host file and user action to spread; a worm self-replicates across networks independently.

Ransomware

Malware that encrypts a victim's files and demands payment for decryption.

Botnet

A network of infected 'zombie' devices remotely controlled by an attacker, often used for DDoS attacks.

Rootkit

Malware that hides deep in a system to give attackers stealthy, persistent, privileged access.

Try an AP-style question

What type of malware is this?

1. Adware
2. Worm
3. Trojan
4. Virus