What is a computer virus | Type of computer virus | Computer virus names

What is a Computer Virus :

A computer virus is a type of malicious program, script or macro designed to cause damage, steal personal information, modify data, send e-mail, display messages, or some combination of these actions. Computer viruses never occur naturally. They are always induced by people. Once created and released, however, their diffusion is not directly under human control.

 After entering a computer, a virus attaches itself to another program in such a way that execution of the host program triggers the action of the virus simultaneously. It can self-replicate, inserting itself onto other programs or files, infecting them in the process. Not all computer viruses are destructive though. However, most of them perform actions that are malicious in nature, such as destroying data. Some viruses wreak havoc as soon as their code is executed, while others lie dormant until a particular event (as programmed) gets initiated, that causes their code to run in the computer.

The Creeper virus was the first virus detected on ARPANET, in the early 1970s, Written by Bob Thomas of BBN Technologies and spread through DEC PDP-10 displaying the message, "I'm the creeper, catch me if you can!".

The Elk Cloner, written in 1982 by the 15-year-old rich skrenta of pittsburgh, was a Boot-Sector virus designed to infect Apply || computers and was the first to detected in the wild.

Brain, created in Pakistan in 1896, was the first PC virus to be found in the wild 

Also, read: Deep web Vs Dark web | How to access Dark web

How does a Computer virus reach you?

Different type of computer viruses reaches at you through the typical web activities.

1. Opening email attachments from fake accounts.

2. Clicking an inappropriate advertisement and link without understanding fully.

3. Installing or Downloading the free games, toolbars or System utilities firm any website.

4. Visiting an infected web page.

5. Inserting or Connecting the infected device and disk.

6. Installing pirated software.

7. Setting up of software without licensing agreements.

Types of Computer Viruses :

There's a lot type of computer viruses exist here, thus we can't mention everyone but here is a list of the famous type of computer viruses...

1.Boot sector Virus 

A Boot Sector is the part of our PC's hard drive that loads our computer's operating system. When a system has booted the code in a boot sector will always run first.

Also, read: What is Botnet and how it works...

A Boot Sector(also known as Boot infector or MBR virus) infects the Master Boot Record(MBR), so the virus loads on the computer memory during startup. 

This virus is attached with our system files i.e. ".exe", ".com" or ".dll"(Dynamic link libraries) files. When the user uses these files, the virus performs destructive operations and destroy all data files.

Boot Sector Virus Examples :

Here is an example of a few most vulnerable Boot Sector Virus...

Anti Exe.

Polyboot.
Brain.
Parity Boot.

2.Macro Virus

First of all, we have to know about what's Macro, Well Macro is a set of recorded keystrokes, Mouse movements and so on that are designed to make your life easier, reduce repetitive typing and so on.

A Macro Virus is a type of Computer virus that hides within the macros used in a program(like as MS Word, MS Excel,etc.).Macro is an executable program thus it can be infected by viruses just like other executable programs.
What's unique about a Micro Virus is user typically don't suspect that a document will contain a virus. Whenever the user opens such files The Micro Virus perform pre-define destructive functions. These viruses may change or erase all the data of any document.

Also, read: How to be an Ethical hacker and start your hacking carrier...

Micro Virus Examples : 

Here's an example of a few Micro Viruses which are most vulnerable...

Relax. 

Bablas. 

Y2K.

3.Memory Resident Virus 

That is a type of virus which infect RAM memory and also hide and store itself within the Computer memory which then allow it to infect any file that is run by Computer, depending on virus programming. 

It can execute whenever the os load and the worst part is that it can execute even when you remove the original infected program or no longer running. 

Resident Virus Example :

CMJ.

Meve.

MrKlunky.

Randex.

4. File Virus

File Virus ( Parasitic Virus)  use an arbitrary existing file as Host. Usually, the virus prepends the body of its code to the beginning of the file or append the body of it's code to the end of the host file,  in which case the original file contents remain intact except the original entry point(OEP) is modified.

The simplest File Virus works by locating a type of file they know how to infect (usually a file name ending by .com or .exe and .dll files also) and overwriting part of the program they are infecting. When the program is executed, the virus code executed and infect more files, after the execution of its code the control return back to the main program and its execution is not even noticed thus everything appears normal. It's also called Parasitic Virus because it leaves no file intact but also leave host functional.  

Examples of File Viruses :

Cascade.
Jerusalem. 

5.Multipartite Virus 

This is a fast-moving virus and a kind of virus which can infect and spread in multiple ways. It can infect both Programs and System Sectors.

Multipartite Virus increases their chance of spreading within the computer by combining feature from both the File Virus and the Boot-Sector Virus thus these viruses easily infect both files and boot sectors simultaneously allowing them to act quickly and spread rapidly, Because of this, the chance of spreading the virus is increased.

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The Multipartite Virus are often tricky and hard to eliminate.

The worst part is that even if you've succeeded in removing all the infected files from your computer, the virus still is hidden in boot-sector and ready to strike again as soon as you boot your system, and if you clean the boot-sector then and the files is still infected then the virus will re-infect the boot-sector by jumping from one of the infected files.

Example of Multipartite Virus :

Junkie Virus.

Tequila Virus.

Invader Virus.

Also, read - What's Firmware and how it works...

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