thinQmaster Virtual testing partner Adaptive practice exams that find your weak spots and drill them. Every answer explained. From $69
Enroll

thinQmaster

Find your exam

Five questions free, before you decide.

Step 1 · choose a vendor

In one of our camps? Your practice exams come with the tuition — they are on your study page already.

Commonly confused · Security Fundamentals & Crypto

Virus vs Worm vs Trojan: What's the Difference?

A virus attaches to a host file and needs a user to run it to spread, a worm is standalone and self-propagates across networks without user action, and a trojan disguises itself as legitimate software to trick users into installing it but does not self-replicate.

vsvs

Trojan

VirusWormTrojan
Needs a host file?YesNoNo, it is its own program
Self-replicates?Yes, when the host runsYes, automaticallyNo
Needs user action?YesNoYes, user installs it
Spread methodInfected files, macros, mediaNetwork vulnerabilities, shares, emailSocial engineering, fake downloads
Famous examplesCIH (Chernobyl), Michelangelo (boot sector)WannaCry, Conficker, SQL SlammerZeus, Emotet loaders, RATs
Key indicatorModified executables or documentsSudden network-wide spread and bandwidth spikesUnexpected remote access or backdoor
Remember it

Virus hitchhikes, worm walks on its own, trojan wears a disguise.

Exam tip

If the scenario says malware spread across the network overnight with no user interaction, choose worm. A free game that installs a backdoor is a trojan (often a RAT).

Tested on

More Security Fundamentals & Crypto look-alikes