That would be the worm and the love bug, one of the most famous worm-like infections
A virus cannot reinvent itself without the help of a 'hosts' living cell. Once the virus invades the living cell it takes over the mechanism of reproduction using the cells enzymes and other chemical to reproduce. Therefore a virus cannot reproduce independently. Once the host cell is compromised the virus is free to infect other cells in the living organism.
No. Virus need to rely on hosts to reproduce.
Actually "every being serves a purpose" the concept of good does not enter into it. Even if "good" entered into the issue to whom does the goodness apply to?A virus exists to duplicate itself. (Good for the virus)A virus that causes immediate death weeds out the genetic line of hosts that die too quickly to allow it to replicate itself and infect other hosts (Good for the virus, more resilient hosts in the future: Bad for the hosts that die but good for the hosts that live and their children)
A virus is a piece of code that attaches itself to a program or file so it can spread from computer to computer. A worm, like a virus, is designed to copy itself from one computer to another, but it does so automatically.
A piece of code that attaches itself to a file to spread itself from computer to computer.
Viruses do not reproduce since they are not alive but they hijack the host's DNA to make more viruses.
A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user.
Some of them can. It depends on the virus and the replication method.
Virus and worms.
A Trojan is a worm that is usually disguised as a desirable download that when executed drops other worms on your computer. Hence the name Trojan horse. A Trojan is not technically a virus because it cannot reproduce itself.
A computer virus is a computer program that can copy itself and infect a computer without the permission or knowledge of the owner.
A virus is a small piece of software that piggybacks on real programs. For example, a virus might attach itself to a program such as a spreadsheet program. Each time the spreadsheet program runs, the virus runs, too, and it has the chance to reproduce by attaching to other programs Courtesy: howstuffworks.com