Glossary
Malware
Malware is software designed to harm a computer or its owner: viruses, spyware, trojans, worms and similar programs.
What it means
Malware is software designed to harm a computer or its owner: viruses, spyware, trojans, worms and similar programs. It usually arrives disguised as something useful — a free download, an attachment, a pop-up warning that your computer is infected — and once it runs, it can steal passwords, watch what you type, show unwanted advertising, or hand control of your computer to someone else. Most malware is not dramatic: it works quietly, and its victim may not notice it for weeks.
How it works
The main types do different jobs. A virus attaches itself to other programs and spreads when they run. A trojan pretends to be legitimate software and opens a way in. Spyware watches what you do — keystrokes, browsing, credentials — and sends it to the attacker. A worm spreads on its own from one computer to another across a network. Adware floods you with advertising. A keylogger records keystrokes, which is how passwords and card numbers are captured. The signs of infection are familiar — sudden slowness, unfamiliar programs, pop-ups you did not ask for, a battery draining faster than usual — but most of those signs also have innocent causes, which is why the response should be proportionate: scan with a reputable security program, update your software, and get professional help if it continues.
Example
Imagine a fictional user, Tom, who downloads a free photo editor from a site he found in a search result. The editor works — but it also installs a program that records his keystrokes and sends them to an attacker. Tom notices nothing until his email account is logged into from another country. The download was the malware's disguise: legitimate-looking software with a hidden second job. The protection that would have caught it was simple — download software only from the developer's official site or a trusted store, and keep a reputable security program running.
Common misunderstandings
The most common misunderstanding is believing that a slow computer means an infection. It usually does not — age, a full disk, or a heavy program are far more likely causes. The opposite mistake is believing that a computer with no symptoms is clean: well-made spyware is designed to be invisible. Symptoms are a reason to check, not a verdict — and the absence of symptoms is not a guarantee.
Related terms
Learn more
- Malware awareness
- What is ransomware?
- How to recognize online scams
- Cybersecurity Awareness Path
- Back to the full glossary
Last checked: 14 November 2026.
Frequently asked questions
How do I know if my computer has malware?
Look for sudden slowness, unfamiliar programs, pop-ups you did not ask for, or a battery draining much faster than usual — but remember most of those signs have innocent causes. The reliable check is a scan with a reputable security program, not a guess from the symptoms.
Can my phone get malware too?
Yes. Phones get malware mainly through apps installed from outside the official stores, malicious links, and fake apps that imitate real ones. Installing apps only from the official store and keeping the phone updated are the two habits that matter most.
What should I do if I suspect malware?
Do not enter passwords on the affected device. Run a scan with a reputable security program you already trust, update your software, and if the problem continues, get professional help. Never download a cleaner advertised in a pop-up — that is itself a classic malware trick.