Malware cheat sheet
Virus
Attaches to a file or program. Needs the user to RUN something to spread. Most often spread by sharing infected files.
Worm
Self-replicates and spreads on its own across a network. Does NOT need a user to do anything.
Trojan
Disguised as something legitimate, like a free game or a software update. Tricks the user into running it.
Ransomware
Encrypts or locks files and demands payment to unlock them. Attacks AVAILABILITY.
Spyware
Secretly monitors what the user does: keystrokes, screenshots, browsing, sometimes the camera or microphone. Attacks CONFIDENTIALITY.
Rootkit
Hides malicious activity from the operating system. Designed so antivirus and the user cannot see it is there. Hard to detect, hard to remove.