A computer virus is a set of instructions or a malicious program which is positioned in a computer so that the computer stops working properly. Computer viruses are mostly self replicating in nature as they create their own copy in other executable files and makes them infected. So, computer virus spreads by self multiplying itself.
Creating Computer Virus
Computer virus are created with a purpose to infect exposed computer system and take hold of administration privileges to access user’s important and critical data. Computer viruses are designed by hackers with an intention to trick people. They make online users their victim. The very first computer virus was developed by Robert Thomas in the year 1971 and named it as “Creeper Virus.” The Program by Thomas infected ARPANET mainframes. Infected mainframes displayed the message, “I’m the creeper: Catch me if you can.”
Elk Cloner virus developed by a teenager Richard Skrenta in the year 1982, was the first wild computer virus where course of action was tracked. Apple II operating systems were infected by Elk Cloner virus through Floppy disks. Computer viruses were developed to trick computer and people but at the same time it showed how harmful programs can be installed in computers to infect them and degrade their performance.
In 1983 Fred Cohen first time coined the term Computer virus for this kind of malicious programs.
How Computer Virus Spreads
Computer virus spreads online through emails, attachments with emails, clicking on infected links, opening an infected website, infected advertisements, clicking executable files etc. computer virus also spreads by connecting removable storage devices or USB drives which are already infected.
Types of Computer Viruses
Computer viruses are of different forms and affect and infect the computer system in different ways. Below is a list of some common computer viruses:
Boot Sector Virus: This virus infects the master boot record. It is difficult and a Tricky task to eliminate the virus. Mostly the system needs to be formatted. It mostly it spreads via removable media.
Direct Action Virus: Also known as non-resident virus. It gets installed and is hidden in the computer memory. It infects and attaches itself to a specific type of files. User experience and system performance is not affected by this virus.
Resident Virus: Resident virus get installed on the computer System and is difficult to identify and remove a resident virus. The version of resident virus stored in memory can be activated even after original virus is deleted. Resident viruses are dangerous because they hide in system’s RAM memory and are not noticed by antivirus and anti-malware software.
Multipartite Virus: The multipartite virus infects the boot sector as well as executable files at the same time. This virus spreads via multiple ways.
Polymorphic Virus: it is difficult for traditional anti-virus programs to identify the polymorphic virus, because changes its signature on replication.
Overwrite Virus: The overwrite virus spreads through emails and it deletes all the files that it infects. To get rid of this virus, one must delete all the infected files. The user loses all the contents because of overwrite virus.
Spacefiller Virus or Cavity Viruses: This virus fills up the blank spaces between the codes. It does not cause any harm to the file.
File infectors: File infector virus or parasitic virus normally infects memory and executable files and remain in system for long time. To get rid of this virus we need to use removal software.
Macro viruses: A computer virus written in the same macro language as used for software programs like Microsoft Excel or word processors is called Macro Virus.A sequence of actions start automatically when the application infected with macro virus is opened
Overwrite Viruses: These viruses are designed with a purpose to destroy or ruin data of a file or application. Once the virus attacks a computer it starts overwriting files with its own code. This virus should be dealt seriously as it can damage sensitive data and is capable to systematically overwriting all files on an infected device. This virus can also install a new code to spread the virus.
Polymorphic Viruses: Polymorphic viruses are capable to alter or recast their code while their basic functions and features remain unaltered. So, they can easily escape detection by anti-virus software. Cyber criminals majorly use and depend on the polymorphic virus.
Rootkit Viruses: The rootkit virus is a malicious program which covertly installs an illicit rootkit on a vulnerable system to open the route for hackers and attackers and provides them total control of the system. The attacker can modify or disable functions and programs of the infected system.
The Bottom Line
In the present time computer virus is a common term that people are aware of. In this article, we have explained computer virus in detail. Also, you must know that a big population indulged in developing viruses and is in hacking profession. So, while using a computer system we must take proper care that the system being used has good and updated antivirus protection. That means systems are installed with licensed antivirus to identify and handle malicious programs known as Computer Virus.
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