Types of Computer Virus

Adware: *A form of spyware that collects information about the user in order to display
advertisements in the Web browser based on the information it collects from the user's
browsing patterns.
Software that is given to the user with advertisements already embedded in the

Malware: *Short for malicious software, software designed specifically to damage or
disrupt a system, such as a virus or a Trojan horse.
Script Kiddie: *A person, normally someone who is not technologically sophisticated,
who randomly seeks out a specific weakness over the Internet in order to gain root access
to a system without really understanding what it is s/he is exploiting because the
weakness was discovered by someone else. A script kiddie is not looking to target specific
information or a specific company but rather uses knowledge of a vulnerability to scan
the entire Internet for a victim that possesses that vulnerability.
Spyware: *Any software that covertly gathers user information through the user's
Internet connection without his or her knowledge, usually for advertising purposes.
Spyware applications are typically bundled as a hidden component of freeware or
shareware programs that can be downloaded from the Internet; however, it should be
noted that the majority of shareware and freeware applications do not come with
spyware. Once installed, the spyware monitors user activity on the Internet and transmits
that information in the background to someone else. Spyware can also gather
information about e-mail addresses and even passwords and credit card numbers.
Spyware is similar to a Trojan horse in that users unwittingly install the product when
they install something else. A common way to become a victim of spyware is to download
certain peer-to-peer file swapping products that are available today.
Aside from the questions of ethics and privacy, spyware steals from the user by using the
computer's memory resources and also by eating bandwidth as it sends information back
to the spyware's home base via the user's Internet connection. Because spyware is using
memory and system resources, the applications running in the background can lead to
system crashes or general system instability.
Because spyware exists as independent executable programs, they have the ability to
monitor keystrokes, scan files on the hard drive, snoop other applications, such as chat
programs or word processors, install other spyware programs, read cookies, change the
default home page on the Web browser, consistently relaying this information back to the
spyware author who will either use it for advertising/marketing purposes or sell the
information to another party.
Licensing agreements that accompany software downloads sometimes warn the user that
a spyware program will be installed along with the requested software, but the licensing
agreements may not always be read completely because the notice of a spyware
installation is often couched in obtuse, hard-to-read legal disclaimers.
Trojan: *A destructive program that masquerades as a benign application. Unlike
viruses, Trojan horses do not replicate themselves but they can be just as destructive.
One of the most insidious types of Trojan horse is a program that claims to rid your
computer of viruses but instead introduces viruses onto your computer.
The term comes from a story in Homer's Iliad, in which the Greeks give a giant wooden
horse to their foes, the Trojans, ostensibly as a peace offering. But after the Trojans drag
the horse inside their city walls, Greek soldiers sneak out of the horse's hollow belly and
open the city gates, allowing their compatriots to pour in and capture Troy.
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 man made. 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
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.
Worm: *A program or algorithm that replicates itself over a computer network and
usually performs malicious actions, such as using up the computer's resources and
possibly shutting the system down.
* Definitions provided by Webopedia