Computer Virus

Computer virus is a harmful software program written intentionally to enter a computer without the user is permission or knowledge. It has the ability to replicate itself, thus continuing to spread. Some viruses do little but replicate, while others can cause severe harm or adversely affect the program and performance of the system. A virus should never be assumed harmless and left on a system.

Type of VIRUS

There are different types of viruses which can be classified according to their origin, techniques, types of files they infect, where they hide, the kind of damage they cause, the type of operating system, or platform they attack. Let us have a look at few of them.

Memory Resident Virus
These viruses fix themselves in the computer memory and get activated whenever the OS runs and infects all the files that are then opened. It can corrupt files and programs that are opened, closed, copied, renamed, etc.

Examples: Randex, CMJ, Meve, and MrKlunky

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. It is a file-infecter virus.

Examples: Vienna virus

Overwrite Viruses
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. The virus replaces the file content. However, it does not change the file size

Examples: Way, Trj.Reboot, Trivial.88.D

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.

Trojans
Trojans or Trojan horses, unlike viruses, do not reproduce by infecting other files, nor do they self-replicate like worms. In fact, it is a program which disguises itself as a useful program or application.

Directory Virus
Directory viruses (also called Cluster Virus/File System Virus) infect the directory of your computer by changing the path that indicates the location of a file. When you execute a program file with an extension .EXE or .COM that has been infected by a virus, you are unknowingly running the virus program, while the original file and program is previously moved by the virus. Once infected, it becomes impossible to locate the original files.

Protection:

Install an antivirus scanner and also download Firewall.

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