Unlike
biological viruses, computer viruses do not simply evolve by themselves
computer viruses do not come into existence spontaneously, nor are they
likely to be created by bugs in regular programs. They are deliberately
created by programmers, or by people who use virus creation software.
Computer viruses can only do what the programmers have programmed them
to do.
Virus writers can have
various reasons for creating and spreading malware. Viruses have been
written as research projects, pranks, vandalism, to attack the products
of specific companies, to distribute political messages, and financial
gain from identify theft, spyware, and cryptoviral extortion. Some virus
writers consider their creations to be works of art, and see virus
writing as a creative hobby. Additionally, many virus writers oppose
deliberately destructive payload routines. Some viruses were intended as
“good viruses”. They spread improvements to the programs they infect,
or delete other viruses. These viruses are, however, quite rare, still
consume system resources, may accidentally damage systems they infect,
and, on occasion, have become infected and acted as vectors for
malicious viruses. A poorly written “good virus” can also inadvertently
become a virus in and of itself (for example, such a ‘good virus’ may
misidentify its target file and delete an innocent system file computer
owner. Since self-replicating code causes many complications, it is
questionable if a well-intentioned virus can ever solve a problem in a
way that is superior to a regular program that does not replicate
itself.
Releasing computer viruses (as well as worms) is a crime in most jurisdictions.
Effects of computers viruses
Some
viruses are programmed to damage the computer by damaging programs,
deleting files, or reformatting the hard disk. Others are not designed
to do any damage, but simply replicate themselves and make their
presence known by presenting text, video, or audio messages. Even these
benign viruses can create problems for the computer user. They typically
take up computer memory used by legitimate programs. As a result, they
often cause erratic behavior and can result in system crashes. In
addition, many viruses are bug-ridden, and these bugs may lead to system
crashes and data loss.