Virus
A computer virus is a program that can replicate itself and spread from one to another computer.
It is embedded within (hidden inside) another program/file called “host” and becomes active when the host is activated on the infected system.
The host can be another computer program, file, e-mail, or document (e.g. Word macro)
Viruses often cause harm to computer data or performances. Some viruses, however, do nothing beyond reproducing themselves.
The infected programs/files spread viruses via
Hard disks, floppy disks, CDs/DVDs, flash drives
Email and Email attachments
Files downloaded from Internet