Computer virus:
A computer virus is a program which can multiplicate and replicate itself. There are
also many virus programs which couldn't replicate but produce huge damage such as adware
and spyware.
What does a virus do?
A computer virus is as similar to normal virus in terms of power to distruct and
replicate. A virus attacks main program or changes its function i.e when a program effects with
a virus it does not behave as before and it produces different data which damage other
programs running. This creates large amount of unwanted programs and disturb computer
important functions. Due to this data gets dislocated or damaged and system primary
programs(boot programs, organizing programs etc)gets disturbed and the computer gets
damaged.
Where does viruses attack, store:
Inorder to get replicated,virus should be attached to the code which is frequently
executed. In a computer, system programs are those which frequently gets executed and all
codes which execute will relate to system programs ,hence virusess will be present where
OS(operating system) is installed i.e in many systems it is C: drive. Due to this reason data
present in c: drive gets spoiled quickly than other data in computer.
Types of viruses:
1. Trojan Horse:
Trojan horses are specially designed by user
to do specific task. It silently gets in to the
program and when executed it does
undesired functions. A Trojan Horse neither
replicates nor copies itself, but causes
damage or compromises the security of the
computer. A Trojan Horse must be sent by
someone or carried by another program and
may arrive in the form of a joke program
or software of some sort. The malicious functionality
of a Trojan Horse may be anything undesirable for a computer user, including data destruction
or compromising a system by providing a means for another computer to gain access, thus
bypassing normal access controls.
2. Worms:
A worm is a program that makes and facilitates the distribution
of copies of itself; for example, from one disk drive to another, or
by copying itself using email or another transport mechanism.
The worm may do damage and compromise the security of the
computer. It may arrive via exploitation of a system vulnerability
or by clicking on an infected e-mail.
3. Bootsector Virus:
A virus which attaches itself to the boot
programs or the place in hard disk where boot
sector programs are stored. These are
normally spread by floppy disks.
4. Macro Virus:
Macro viruses are viruses that use another
application's macro programming language to
distribute themselves. They infect documents
such as MS Word or MS Excel and are
typically spread to other similar documents.
5. Memory Resident Viruses:
Memory Resident Viruses reside in a
computers main or primary memory (RAM).
They are initiated from a virus which runs on
the computer and they stay in memory after
it's initiating program closes.
6. Rootkit Virus:
gain control of someone's computer.A rootkit
virus is an undetectable virus which attempts
to allow someone to gain control of a
computer system. The term rootkit comes
from the linux administrator root user. These
viruses are usually installed by trojans and are
normally disguised as operating system files.
7. Polymorphic Viruses:
A polymorphic virus not only replicates itself
by creating multiple files of itself, but it also
changes it's digital signature every time it
replicates. This makes it difficult for less
sophisticated antivirus software to detect.
by creating multiple files of itself, but it also
changes it's digital signature every time it
replicates. This makes it difficult for less
sophisticated antivirus software to detect.
8. Logic Bombs/Time Bombs:
initiate at a specific date or when a specific
event occurs. Some examples are a virus
which deletes your photos on Halloween, or a
virus which deletes a database table if a
certain employee gets fired.
9. Companion Viruses:
Companion viruses can be considered as a
type of file infector virus, like resident or direct
action types. They are known as companion
viruses because once they get into the system
they ccompany with other files that already
exist and help them to carry there actions
more effectively.These generally use the
same filename and create a different extension
of it. For example: If there is a file "Me.exe",
the virus creates another file named "x.com" and hides in the new file. When the system calls
the filename "x", the ".com" file gets executed (as ".com" has higher priority than ".exe"), thus
infecting the system.
10. FAT virus:
the information about the location of files, available space,
unusable space, etc. FAT virus attacks the FAT section and
may damage crucial information. It can be especially
dangerous as it prevents access to certain sections of the
disk where important files are stored. Damage caused can result in loss of information from
individual files or even entire directories.
11. Web Scripting Virus:
Many web pages include complex codes in
order to inorder to perform some desired
function .When this code is exploited or
accessed from system it creates undesirable
actions.The main sources of web scripting
viruses are the web browsers or infected web
pages.
12. Multipartite Virus:
These viruses spread in multiple ways possible.
It may vary in its action
depending upon the operating system installed and the presence of
certain files.In the initial phase, these viruses tend to hide in the
memory as the memory resident viruses do, then they infect the hard
disk.
depending upon the operating system installed and the presence of
certain files.In the initial phase, these viruses tend to hide in the
memory as the memory resident viruses do, then they infect the hard
disk.
13.Overwrite Viruses:
These type of virus deletes data when effects a
file. After its
action the file becomes totally useless. The virus replaces the
file content. However, it does not change the file size.
action the file becomes totally useless. The virus replaces the
file content. However, it does not change the file size.
14.Spyware:
Spyware is software that aids in gathering
information about a
person or organization without their knowledge and that may send
such information to another entity without the one notice or that
asserts control over a computer without the consumer's knowledge.
person or organization without their knowledge and that may send
such information to another entity without the one notice or that
asserts control over a computer without the consumer's knowledge.
Spyware is mostly classified into four types:
1: system monitors
2: trojans
3: adware
4: tracking cookies
Spyware is mostly used for the purposes such as ; tracking and storing internet
users movements; serving up pop-up ads to internet users.
Whenever spyware is used for malicious purposes, its presence is typically hidden from the
user and can be difficult to detect. Some spyware, such as keyloggers, may be installed by the
owner of a shared, corporate, or public computer intentionally in order to monitor users.
Source: wikipedia
Good post.sharing the Difference among Virus,Worm,Trojan and Bots
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