A potentially damaging computer programme capable of reproducing itself
causing great harm to files or other programs without permission or
knowledge of the user.
Virus - A program that when run, has the
ability to self-replicate by infecting other programs and files on your
computer. These programs can have many effects ranging from wiping your
hard drive, displaying a joke in a
small box, or doing nothing at all except to replicate itself. These
types of infections tend to be localized to your computer and not have
the ability to spread to another computer on their own. The word virus
has incorrectly become a general term that encompasses trojans, worms,
and viruses.
Types of viruses :-
The different types of viruses are as follows-
1) Boot Sector Virus :- Boot sector viruses infect either the master
boot record of the hard disk or the floppy drive. The boot record
program responsible for the booting of operating system is replaced by
the virus. The virus either copies the master boot program to another
part of the hard disk or overwrites it. They infect a computer when it
boots up or when it accesses the infected floppy disk in the floppy
drive. i.e. Once a system is infected with a boot-sector virus, any
non-write-protected disk accessed by this system will become infected.
Examples of boot- sector viruses are Michelangelo and Stoned.
2) File or Program Viruses :-Some files/programs, when executed, load
the virus in the memory and perform predefined functions to infect the
system. They infect program files with extensions like .EXE, .COM, .BIN,
.DRV and .SYS .
Some common file viruses are Sunday, Cascade.
3) Multipartite Viruses :-A multipartite virus is a computer virus that
infects multiple different target platforms, and remains recursively
infective in each target. It attempts to attack both the boot sector and
the executable, or programs, files at the same time. When the virus
attaches to the boot sector, it will in turn affect the system’s files,
and when the virus attaches to the files, it will in turn infect the
boot sector.
This type of virus can re-infect a system over and over again if all parts of the virus are not eradicated.
Ghostball was the first multipartite virus, discovered by Fridrik Skulason in October 1989.
Other examples are Invader, Flip, etc.
4) Stealth Viruses :-These viruses are stealthy in nature means it uses
various methods for hiding themselves to avoid detection. They
sometimes remove themselves from the memory temporarily to avoid
detection by antivirus. They are somewhat difficult to detect. When an
antivirus program tries to detect the virus, the stealth virus feeds the
antivirus program a clean image of the file or boot sector.
5)
Polymorphic Viruses :-Polymorphic viruses have the ability to mutate
implying that they change the viral code known as the signature each
time they spread or infect. Thus an antivirus program which is scanning
for specific virus codes unable to detect it's presense.
6)
Macro Viruses :- A macro virus is a computer virus that "infects" a
Microsoft Word or similar application and causes a sequence of actions
to be performed automatically when the application is started or
something else triggers it. Macro viruses tend to be surprising but
relatively harmless.A macro virus is often spread as an e-mail virus.
Well-known examples are Concept Virus and Melissa Worm.
If you
use a computer, read the newspaper, or watch the news, you will know
about computer viruses or other malware. These are those malicious
programs that once they infect your machine will start causing havoc on
your computer. What many people do not know is that there are many
different types of infections that are categorized in the general
category of Malware.
Malware - Malware is programming or files
that are developed for the purpose of doing harm. Thus, malware includes
computer viruses, worms, Trojan horses, spyware, hijackers, and certain
type of adware.
This article will focus on those malware that
are considered viruses, trojans, worms, and viruses, though this
information can be used to remove the other types of malware as well. We
will not go into specific details about any one particular infection,
but rather provide a broad overview of how these infections can be
removed. For the most part these instructions should allow you to remove
a good deal of infections, but there are some that need special steps
to be removed and these won't be covered under this tutorial.
Before we continue it is important to understand the generic malware terms that you will be reading about.
Backdoor- A program that allows a remote user to execute commands and
tasks on your computer without your permission. These types of programs
are typically used to launch attacks on other computers, distribute
copyrighted software or media, or hack other computers.
Hijackers- A program that attempts to hijack certain Internet functions
like redirecting your start page to the hijacker's own start page,
redirecting search queries to a undesired search engine, or replace
search results from popular search engines with their own information.
Spyware- A program that monitors your activity or information on your
computer and sends that information to a remote computer without your
Knowledge.
Adware- A program that generates popups on your
computer or displays advertisements. It is important to note that not
all adware programs are necessarily considered malware.
There
are many legitimate programs that are given for free that display ads in
their programs in order to generate revenue. As long as this
information is provided up front then they are generally not considered
malware.
Dialler - A program that typically dials a premium
rate number that has per minute charges over and above the typical call
charge. These calls are with the intent of gaining access to
pornographic material.
Trojan- A program that has been designed
to appear innocent but has been intentionally designed to cause some
malicious activity or to provide a backdoor to your system.
Worm- A program that when run, has the ability to spread to other
computers on its own using either mass-mailing techniques to email
addresses found on your computer or by using the Internet to infect a
remote computer using known security holes.
