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.
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.
