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Types of computer virsues

Definition:

Computer virus is software that interrupts the routine and sequential tasks of computer system and without the permission of computer user and programmer

Or
It is a master program that automatically penetrate sin the hard disk tracks and erases that stored data or encrypts the executable files.

Properties

There are different properties of the computer viruses; each of these viruses has the capability to replicate them self back which makes them most dangerous. These types of programs can travel through the entire system and can harm the windows system and dynamic link files directly. some viruses has little power to travel but some are extremely harmful for the computer system and can block the hard disk from getting free from the infection.in this kind of situation there is no other way instead of replacing the hard disk.

Types of Viruses:

There are several kinds of viruses each with different properties to infect the computer system. The most commonly use types are listed below:

Resident viruses
Direct action viruses
Over write viruses
Boot viruses
File infectors
Macro viruses

Resident Viruses:
These are the threat programs that permanently penetrates in the Random access memory of the computer system .when the computer gets started it is automatically transmitted to the secondary storage media and interrupts all the sequential operations of the processor and corrupt all the running programs. For instance Randex and CMJ are commonly known resident viruses .if these viruses gets into the hard disk then one has to replace the secondary storage media and some times RAM even.

Direct Viruses:
This virus has the ability to replicate back automatically to the concerned executable form which is automatically created at the start up of the computer system.The name specifies they directly affect the master program or operating system of the computer system making hardware stuck during the start up and removes the system files from the windows folder. You have often seen the unknown file with AUTO.BAT name. In the system file folders this is an indication that computer system has direct virus in it. This file is always located in the root directory of windows and interrupts the operations of operating system.

Overwrite Viruses:
These kinds of viruses automatically overwrite the located files in the computer system and infect them, making them useless. When some one opens these infected in place of information small rectangular boxes appears. The only possible way to save the remaining files from infection is to completely remove these files from the directory. The most commonly known overwrite viruses are Trojan, trivial, reboot, boot.

Boot Virus:
Boot virus is a threat program that directly affects the boot up process when computer is started. When boot strapper loads the operating system program from hard disk to RAM this virus is automatically loaded to the RAM and ties up it self to the hared disk. The major source of this virus I s the corrupt media files, infected compact disks and insecure internet connections. Examples of boot viruses are polyboot and antiexe.

Macro Virus:
Other famous types of virus is macro virus .this is program that infects created or stored applications in the computer system such as Microsoft office, adobe programs and other useful application programs. The symptoms of infection include the automatic restart of computer again and again. Commonly known types of macro viruses are Melissa A, Bablas and Y2K Bug.

File Infectors:

Another common problem of the computer programmers is the file infector viruses which automatically interrupt during the processing or while writing and infects the file. Or they work on execution of the file. Unwanted dialog boxes starts appearing on the screen with unknown statements with extensions .com and .exe. They destroy the original copy of the file and save the infected file with the same as original. Once infected, it is very hard to recover the original data.