Topics: Computer virus, Boot sector, Master boot record Pages: 8 (1576 words) Published: December 17, 2014

Computer virus is a software program written
with malicious intentions. There are number of
computer viruses that can impede the
functioning of your computer system. 


They are replicated by themselves. Viruses are so
dangerous and malicious that they can be automatically
copied and pasted from memory to memory over and over;
the transmitting power is too much quick from network to
network that can simply hang smoothly running computer,
sometimes damage the important programs of the
computer. Viruses are very dangerous program can go on
their activities automatically and can do a great loss of the users.

Memory Resident Virus
 Direct Action Virus
 Overwrite Viruses
 Boot Sector Virus
 Macro Virus
 Directory virus
 Polyphormic Virus
 Companion Virus
 FAT Virus
 Multipartite Virus
 Web Scripting Virus
 Worms
 File Infector Virus

Memory Resident
These viruses fix themselves in the computer
memory and get activated whenever the OS runs
and infects all the files that are then opened.
 Hideout: This type of virus hides in the RAM and
stays there even after the malicious code is
executed. It gets control over the system
memory and allocate memory blocks through
which it runs its own code, and executes the
code when any function is executed.
 Target: It can corrupt files and programs that
are opened, closed, copied, renamed, etc.
 Examples: Randex, CMJ, Meve, and MrKlunky
 Protection: Install an antivirus program.

Direct Action Virus

The main purpose of this virus is to replicate and take action when it is executed. When a specific condition is met, the virus will go into action and infect files in the directory or folder that are specified in the AUTOEXEC.BAT file path. This batch file is always located in the root directory of the hard disk and carries out certain operations when the computer is booted.

FindFirst/FindNext technique is used where the code selects a few files as its victims. It also infects the external devices like pen drives or hard disks by copying itself on them
 .Hideout: The viruses keep changing their location into new files whenever the code is executed, but are generally found in the hard disk's root directory.
 Target: It can corrupt files. Basically, it is a file-infecter virus.  Examples: Vienna virus
 Protection: Install an antivirus scanner. However, this type of virus has minimal effect on the computer's performance.

Overwrite Virus
A virus of this kind is characterized by the fact
that it deletes the information contained in the
files that it infects, rendering them partially or
totally useless once they have been infected.
 Hideout: The virus replaces the file content.
However, it does not change the file size.
 Examples: Way, Trj.Reboot, Trivial.88.D
 Protection: The only way to clean a file
infected by an overwrite virus is to delete the
file completely, thus losing the original content.
 However, it is very easy to detect this type of
virus, as the original program becomes useless.

Boot Sector Virus
This type of virus affects the boot sector of a hard disk.
This is a crucial part of the disk, in which information
of the disk itself is stored along with a program that
makes it possible to boot (start) the computer from the
disk. This type of virus is also called Master Boot
Sector Virus or Master Boot Record Virus.
 Hideout: It hides in the memory until DOS accesses
the floppy disk, and whichever boot data is accessed,
the virus infects it.
 Examples: Polyboot.B, AntiEXE
 Protection: The best way of avoiding boot sector
viruses is to ensure that floppy disks are writeprotected. Also, never start your computer with an unknown floppy disk in the disk drive.

Macro Virus
Macro viruses infect files that are created using certain
applications or programs...
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