Virus
A
program or piece of code
that is loaded onto your computer without your knowledge and runs against
your wishes. Viruses can also replicate themselves. All computer viruses are
manmade.
A
simple virus that can make a copy
of itself over and over again is relatively easy to
produce.
Even such a simple virus is dangerous because
it will quickly use all available memory and bring
the system
to a halt. An even more dangerous type of virus is one capable of transmitting
itself
across networks
and bypassing security
systems.
Since 1987,
when a virus infected ARPANET,
a large network used by the Defense Department and many
universities, many antivirus
programs have become available.
These programs periodically
check your computer
system for the best-known types of viruses.
Some people
distinguish between general viruses and worms.
A worm is a
special type of virus that can replicate itself and
use memory, but cannot attach itself to other
programs.