The first ever computer worm was devised to be an anti-virus software. There's never been a worm with that tough a head or that long a tail!" "You have the biggest-ever worm loose in the net, and it automatically sabotages any attempt to monitor it. In the novel, Nichlas Haflinger designs and sets off a data-gathering worm in an act of revenge against the powerful men who run a national electronic information web that induces mass conformity. The actual term "worm" was first used in John Brunner's 1975 novel, The Shockwave Rider.
Morris worm source code floppy diskette at the Computer History Museum However, as the Morris worm and Mydoom showed, even these "payload-free" worms can cause major disruption by increasing network traffic and other unintended effects. Many worms are designed only to spread, and do not attempt to change the systems they pass through. Worms almost always cause at least some harm to the network, even if only by consuming bandwidth, whereas viruses almost always corrupt or modify files on a targeted computer. Computer worms use recursive methods to copy themselves without host programs and distribute themselves based on the law of exponential growth, thus controlling and infecting more and more computers in a short time. When these new worm-invaded computers are controlled, the worm will continue to scan and infect other computers using these computers as hosts, and this behavior will continue. It will use this machine as a host to scan and infect other computers. It often uses a computer network to spread itself, relying on security failures on the target computer to access it.