Worm
Self-replicating malware that spreads across networks without user interaction.
A worm self-replicates and spreads across networks with no user interaction, typically by exploiting a vulnerable network service — which is what lets it propagate explosively. Because it needs no host file or user action (unlike a virus), the controls that matter are fast patching, network segmentation to contain spread, and disabling unneeded services. WannaCry (exploiting EternalBlue) and Conficker are the textbook examples of worm outbreaks.