Threat Explainers · 6 min read
What Is Malware? Types and How It Spreads
Malware is any software written to act against the interests of the person running it. Everything else — virus, trojan, worm, ransomware — is a subcategory describing either how it spreads or what it does.
Published 2026-08-09 · Last updated 2026-08-09
The main families
Viruses attach to other files and spread when those files are shared. Worms self-propagate across networks without user action. Trojans masquerade as desirable software. Ransomware encrypts data and demands payment. Spyware and infostealers harvest credentials and browsing data. Adware injects advertising. Rootkits hide other malware from the operating system. Cryptominers quietly consume your CPU.
- Virus — attaches to files and spreads with them
- Worm — spreads itself across networks
- Trojan — disguised as legitimate software
- Ransomware — encrypts files for extortion
- Spyware / infostealer — harvests data and credentials
- Adware — injects unwanted advertising
- Rootkit — conceals other malware
- Cryptominer — steals processing power
How it reaches home users today
Pirated software and cracks, fake installers promoted through search advertising, malicious browser extensions, email attachments and links, malvertising on low-quality sites, and USB drives of unknown origin. Classic self-replicating viruses are now a small share of what people actually encounter.
Defences that cover every family
Keep the OS and browser patched, run one resident antivirus, use unique passwords with multi-factor authentication, keep a backup you can restore, and install software only from official sources. Those five habits cover more ground than any product feature list.
Frequently asked questions
- What is the difference between a virus and malware?
- Malware is the umbrella term. A virus is one specific type that spreads by attaching itself to other files.
- Can malware infect a phone?
- Yes, mainly Android devices through apps installed outside the Play Store. iOS is more constrained but not immune.