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Lesson 5 of 8 · 7 min · +100 XP

What are the main types of malware?

Malware is software built to harm you or your device. The main types are worms, which spread by themselves; trojans, which pose as something useful; spyware and infostealers, which steal passwords and data; and ransomware, which locks your files and demands payment. Installing updates promptly closes most of the doors they use to get in.

▶ Try it

Why it matters

Malware types differ in how they spread and what they want. Worms move on their own, trojans wait to be run, infostealers grab saved logins, and ransomware encrypts files and extorts. Patching and endpoint protection cut off the paths they use.

In 7 minutes you'll be able to

  • Worms spread alone, trojans wait to be run, infostealers steal logins, ransomware locks files.
  • Get apps and updates only from official sources, and install updates promptly.
  • Infected? Disconnect, report, and change passwords from a clean device.

What you'll practise

  1. Malware bestiary

    Four creatures, four habits. Sort each sighting into the right family.

    • It jumps from computer to computer on the network without anyone clicking → Worm
    • A free "video converter" that quietly installs something else → Trojan
    • It copies the passwords and cookies saved in your browser → Infostealer
    • Every file turns into gibberish and a note demands payment → Ransomware
    • A cracked game download that comes with a hidden extra → Trojan
    • Shortly after an infection, someone logs in to your email from abroad → Infostealer
    • The shared drive locks up too, not just your laptop → Ransomware
    • It hits thousands of unpatched machines worldwide in a single day → Worm

  2. The "update your player" trap

    This pop-up appears on a free movie site. Tap every red flag.

    HD Video Player
    ⚠️ Your video player is out of date. 3 viruses found on your device!
    This video needs the latest player. Download HD_Player_Setup.exe now.
    Turn off your antivirus during installation.
    Now playing: Pasta in 10 minutes

  3. Infected? Do this

    Your NovaCorp laptop is acting strangely after that download. Put the steps in order.

    1. Disconnect from Wi-Fi and unplug any network cable
    2. Don't pay, and don't type any passwords on that device
    3. Report it to IT or security straight away
    4. Let IT scan or reset the device before using it again
    5. Change your passwords from a different, clean device
    6. Restore lost files from a backup made before the infection

  4. Shut the doors

    Ada's last check: how do you keep malware out in the first place?

    1. "Restart to install updates" pops up in the middle of your work. What do you do?

      • Save your work and restart today (Answer)
      • Postpone it for as long as possible

    2. Where should new apps and updates come from?

      • The official app store, the vendor's site or your device's settings (Answer)
      • Whichever download link appears first in the search results
      • Any site, as long as the download is free

    3. You have antivirus. Is that enough on its own?

      • It helps, but updates, backups and care with downloads matter too (Answer)
      • Yes, antivirus catches everything

Remember

Updates close the doors malware uses. A delayed patch is an open door.

Key facts

  • Ransomware was present in 44% of the data breaches analysed in Verizon's 2025 report, up from 32% the year before. · Source: Verizon, 2025 Data Breach Investigations Report
  • The 2017 WannaCry ransomware spread as a worm through a Windows flaw for which a security update had been released about two months earlier. · Source: UK National Audit Office, Investigation: WannaCry cyber attack and the NHS (2017)
  • A worm spreads between computers without any user action, while a trojan needs someone to run it, usually because it looks like a useful program.
  • Infostealers can copy session cookies as well as passwords, which can let an attacker into an account that is already logged in.

Updated:

Questions people ask

What is the difference between a virus and malware?

Malware is the umbrella term for any harmful software. A virus is one type that attaches itself to other files and spreads when they are opened. Worms, trojans, spyware and ransomware are other types.

How do I know if my phone has malware?

Warning signs include sudden pop-ups, apps you didn't install, a battery that drains fast, and messages sent from your accounts that you didn't write. Remove unknown apps, update the phone, and change important passwords from another device.

Can you get malware just by visiting a website?

It is rare on an up-to-date device, but outdated browsers and plug-ins can be exploited. Most infections still need you to download or run something, which is why fake update pop-ups are so common.

Do I still need antivirus software?

Built-in protection on modern computers and phones is a good baseline for most people. Keep it switched on and updated, and combine it with prompt updates and regular backups.

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