Virus

a software program that is designed to replicate itself, spread from one computer to another, and interfere with computer operation; a computer virus may corrupt or delete data on a user’s computer, use an email program to spread itself to other computers, or even erase everything on a user’s hard disk. Computer viruses can be spread by attachments in email messages or instant messaging messages; disguised as attachments of images, greeting cards, or audio and video files, and hidden in illicit software or programs that are downloaded to a computer.