What is a Computer Virus & Their Types

What is a Computer Virus? :: A Computer Virus is a program or programming code and set of codes that are composed, designed, and written by software Developers or programming engineers to hurt or infect other computers locally or in a PC systems network.

They are capable of contaminating and infecting other PC by duplicating or reproducing itself as a natural biological virus.

A portion of them is innocuous while different viruses can harm or damage the computer system seriously and can harm the computer clients and users to an extent.

What is a Computer Virus
What is a Computer Virus & its Type

Computer viruses can replicate themselves and infect different computer shockingly and without any information to a computer user or client, they can hide and attack aggressively when comes in contact with “HOST”

Computer Virus acts as indicated by the codes or guideline or set of directions written in the program, they are capable of duplicating itself in n number of times till your computer memory goes down which can make the computer system to freeze or stop and quit reacting the booting process of a computer.

Numerous such files or codes are composed and written such that they harm the computer system severely by formatting or erasing essential system files from HARD DISK DRIVES.

They harm, defiles, erases or even rename critical programs, files, and documents of the PC system, for example, .EXE.SYS.DLL .OCX.COM etc

They are spread by utilizing infected or contaminated media when these infected media is taken to the uninfected computer it gets infected or by downloading Documents, videos, pictures, and content from the internet which contains malicious programs.

The Known First computer virus was developed by two Pakistani Brothers from Lahore in 1986 and named ‘BRAIN VIRUS’.

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There are some individuals or even societies which create destructive computer viruses to hurt and harm personal computers or computer networks.

They are truly exceptionally capable and talented software engineers who are utilizing their knowledge, information, skills, and abilities in the wrong directions.

Common Example of Computer Viruses are I love You, Y2K, Jerusalem, kill bill, w3perite and so forth::

What is a Computer Virus
What is a Computer Virus & its Type

Different Types Of Computer Viruses

The computer viruses can be classified in Following types ::

  • System Virus
  • File Viruses
  • Boot Sector or Boot Record Viruses

System Viruses

System Viruses are a computer program or software code that resides and lives inside the system area of the hard disk or any other media which contains MBR (Master Boot Record), they infect the boot area of the system, and various other locations of the operating systems.

They mainly try to infect or contaminate boot files namely command.com, Io.sys, and Msdos. sys are the system files that carry out the boot process of a working operating system.

They basically try to infect the input and output functions of computer systems.

They even can remain or dwell in the system & System Viruses::

They are computer program which resides inside the system area of the hard disk or another media which contains MBR (Master Boot Record), they infect the boot area of system and various other locations of the operating systems.

They mainly try to infect boot files namely command.com, Io.sys and Msdos.sys these are the system files which carries out the boot process of an operating system.

They basically try to infect the input and output functions of computer systems. They even can remain or dwell in the system area & can do its work of contaminating and infecting other system records which are critical and crucial to run the boot procedure of computer system

Trojan Viruses

Trojan Horses is a malicious program designed, developed, planned, and created to harm the computer system.

The codes are customized such that when it interacts with some other program or documents it changes them into the Trojan virus.

They control and perform the task of controlling and manipulating the critical files of the working system it infects and harms File Allocation Table of HARD DISK DRIVES which contains important and crucial data of Computer system [PC].

They are generally used as a computer program and is responsible for the misbehavior of personal computer.

The word Trojan originates from a Greek word which demonstrates the Trojan war, where the officers used to hide themselves inside huge wooden horses.

Trojan Horses are a malicious program that is developed to execute destructive codes for breaking down a computer system.

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Macro Viruses

These are a tiny program that is composed of information files. Which can be attached to any files, for example, text or even graphics, for example, pictures, images, or videos that are not harmful as different other types of viruses.

These types of viruses don’t infect program files, for example, EXE or.COM they contaminate application programs, for example, word or speed sheets.

They are the most widely recognized viruses seen nowadays. They are created to harm application program.

They normally infect computers when you download certain documents from the web and if the document contains malicious program your system gets infected.

Best precautionary measures should be taken such as purchase a good antivirus program that is commonly used this day are Quickheal, Norton, Kaspersky, etc, and update it to its latest available download.

When you are about to download certain files from internet just go and scan these files which are from an unknown source.

Regular scanning of the hard disk must be done, checking and scanning of viruses from removable disk such as DVD CD and pen drives or external Computer Hard disk must be done periodically.


A worm is a bit of code that is customized such that it replicates itself when interacts with other different computers in the network.

Worms more often than not harm computers when connected to each other via networking. These type of viruses which are attached to files or programs and harm or manipulate the system files which are available in your computer systems.

They generally harm the computer which is on the network. Now and again they crash the whole network or infects the hosted data and their functionality, performance is influenced when WORMS are executed.

File Viruses

These programs infect executables files and records such as.EXE and.COM. They at times change the extension of the file and make them useless.

These viruses are attached to the start or the end of the executable files and records, they don’t harm data files and do not make any manipulation Inside the files and usually, change the functionality and performance of the executable files.

They change the programmed code of the executable files and documents. Which are written and composed for a specific, particular and special task to perform and hence abnormal set of instruction is executed when someone runs them

Some of the file viruses are written and developed in such a fashion that at a specific time the programs get activated and runs to delete all executable files present inside a computer,

which harms the computer badly, and hence sometimes computer stops responding or get freeze. Friday 13th & Jerusalem are the types of file viruses.

Boot Sector or Boot Record Viruses

The Boot sector or Boot Record Viruses are additionally called as “PARTITION VIRUS”.The computer starts from the boot area of the hard disk which is 0, 0.1 sector of computer hard disk drive [HDD].

In this sector, vital boot records are stacked which causes a computer to start or boot the operating system.

This code in boot sector stacks in the partition table and PC hard drives have partition table which is a basic part which loads the working operating system.

They can stay active constantly. They infect or harm the startup procedure of computer and can survive warm boots and furthermore contaminates uninfected startup files and when this boot sector infections contaminates startup files which result in boot fails.

As they stay active in memory, therefore, they can be called ‘MEMORY RESIDENCE VIRUS’ these programs or codes contaminate clean startup records and executable files to wreck the boot procedure of the operating system and even can erase the information present in the computer hard disk.

Example:: Golden Gate, Brain virus.

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Removal and Precautions Taken Against Computer Viruses?

They have become smarter these days, and even can make a fool of good antivirus software and are developed by the programmers who want to harm the computer system.

They reside in the memory and do all the functions they have been developed for. They tend to hide themselves in such a fashion that it is very difficult to eliminate them after infection

Viruses enter our Personal Computer when we try to download videos, images, or text online where viruses are attached to these files.

They come in contact with them and infect our computer system. You just need to take some preventive measures before trying to download anything from the internet, or mails. Copying data from a removable disk such as DVD, CD, or pen drives.

Use any legal Antivirus software and update it periodically and scan complete hard disk drives and Removable disks such as pen drives and external hard disk drives for eliminating any kind of virus infection or threat

Never ever try to open or copy data from an unknown source before doing so scan it with a good antivirus program which is updated and can eliminate or remove any malicious program or virus-like activity from your computer system.

  • One Should always use legal antivirus Software.
  • Regular Updates of such antivirus must be done periodically.
  • Never try to open or download from unknown Websites or copy any files, documents, images, videos, and content from infected USB drives and CDs or DVDs.
  • Never visit pornographic websites as they contain a malicious program that can hurt or damage system files or operating system.
  • One must not download pirated software that may contain a malicious program.
  • You must scan any USB medium before using it.
  • Always beware of phishing attacks generally happens when clicked on websites that are not authenticated.

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