Computer viruses are programs that can replicate and spread from one computer to another by using code. They are usually sent over the internet or through a disk drive or memory device.
A computer virus can also be known as malware or spyware.
Malware and spyware viruses can also collect information or data from an infected device and send the information to another device.
Online pop-ups and 'malvertising' (fake advertising) spread viruses when an advert is clicked. These adverts are most commonly informing you have won a prize, recommending you install anti-virus software or can be hidden within emails from unknown senders.