A computer virus is a type of computer program that is
designed to hide in the background and replicate itself
by attaching itself to existing programs or parts of the
operating system. There are now more than 22,000 known computer
virus in circulation throughout the world and more are being
discovered every day. Most folks lump together worms, trojan
horses and viruses under the term "virus", but
they are actually different things. Here
is a site with easily understood definitions for each.
Even a simple virus is dangerous because it can quickly
use all available memory and bring the system to a halt.
Some infected code will perform malicious deeds, like deleting
or scrambling users' files or their entire system, disabling
certain functions, causing erratic system behavior, or transmitting
itself across networks and bypassing security systems.
Users can unknowingly transmit a virus from one system
to another by copying infected program files from one machine
to another or by using an infected program downloaded from
the Internet. One of the most prevalent means of transmitting
viruses is via email. Often times, we receive an email that
looks like it is something we want, but instead it is a
trojan horse containing harmful code. Even if the file comes
from a friend, you still must be sure what it contains before
opening it, because often, a trojan horse will automatically
access your email address book send itself to everyone you
know without your knowlege! When in doubt, ask the sender
before openning an unexpected attachment, and scan it with
a fully updated anti-virus program.Never download an executable
program just to "check it out" - if it's a trojan,
the first time you run it, you're already infected!