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Important Viruses types and recovery
technique
There are many types of viruses, but
the most important types of viruses are described below.
Boot sector virus
We know that the disk
is divided into tracks and sectors the disk on which the
operating system has been loaded, has a special program in
its first sector called the boot sector. When the computer
is turned on, the program in the boot sector is
automatically loaded into the memory. This program then
loads the operating system into the memory after performing
some initial tasks. The boot sector virus modifies the
program in the boot sector. It is loaded into memory
whenever computer is turned on. This virus is attached with
the executable files, i.e. .exe, .com, and .dll files. When
these executable files are used by the user, the virus
attached with these files is also activated. It infects
other files and also performs destructive activities. It
also destroys the data files.
Chernobal Virus
The famous chernobal virus deletes all
the Microsoft Office files and also the partition
information from the disk. Once the partition of the disk is
deleted, the important data on the disk cannot be accessed.
Logic Bomb
Logic bomb is a virus, which is
activated on the basis of a logical condition. Examples of
conditions that can be used as triggers for a logic bomb are
the presence or absence of certain files, a particular day
of the date etc. Once this virus is triggered, the important
data stored into a computer may be deleted or corrupted.
Usually, this type of virus is created
and installed by a programmer who is working in a
organization on temporary basis. He installs the logic bomb
in an accounting program to check for his name in the
organization payroll system. If the employee is terminated,
the logic bomb is triggered and the program may delete files
of payroll system or may perform some destructive actions.
Trojan Horse
Usually, the Trojan Horse virus is the
part of some computer game programs. When game program is
installed in the computer and run, this virus is activated.
An example of Trojan Horse is Format C.
Redlof
Redlof virus is a polymorphic virus. It
is written in visual basic script. Polymorphic means
“changes nature with passage of time”. This virus changes
its nature with passage of time and therefore, it is
difficult to catch this virus by an anti virus program.
Normally, this virus infects the file “Folder.htt”. This
file is the part of windows operating system.
- Some viruses may make invisible
changes, hence corrupting the data being used and some
virus may also make data unusable.
- A virus program may detect some
special information like passwords or any sensitive data
and send it to some other user on a network. For example
a virus program may read the “Pin code” of credit card,
entered by a user and then send this information to
another user.
- A virus may make resources
unavailable to the users. For example a virus after
copying itself on all computers on a network, may affect
the communication activity on the network, so that other
users cannot use the network.
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