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Classification of Computer Viruses / Computer Virus

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Methods of Infection

Computer Virus Classification is easy when you understand the different types.

A Computer Virus is a term used to generically identify a number of types of malicious software programs. These malicious software programs can be classified based on their method of infection. Malicious programs can be identified by their intent to steal information and damage a computer system or network. Computer Viruses belong into two categories Viruses, and Worms. These have then been divided into sub-categories


A virus is a small snippet of code that has no ability to function on its own and needs a host executable or document in order to function, thrive, propagate, and ultimately deliver its payload.

Executable Virus

A virus is a self-replicating program that injects itself into software programs. Once the virus has infected a host program it waits till a pre-determined time to deliver its payload, meanwhile replicating itself throughout the computer or network that it is has penetrated. Executable viruses are no longer as prevalent in current operating system as they once were; though they are still found in the wild on rare occasions.

Macro Virus

A macro virus is a class of infection that infects Microsoft office based products utilizing the embedded functionality of Visual Basic in order to transmit itself throughout a company’s network and e-mail system. This category of virus was seen in the wild during the late 90’s before finally being brought under control through a combination of security updates in Microsoft products, and by enhanced detection methods by anti-virus vendors.

Boot-Sector Virus

Boot sector viruses were notorious in the late 80’s through the late 90’s for being the most difficult to detect, and clean. Their ability to load and then camouflage themselves in order to hide themselves from sophisticated detection techniques allowed them to flourish longer than other types of viruses. In the last 2 years a resurgence of this style of attack has been seen in the wild and often isn’t detected by even the highest rated anti-virus vendors.


A computer worm is a class of computer virus that can propagate itself not only on intranets, but also through external networks such as the internet. A worm can be a stand-alone program that functions independently of a host executable.

Trojan horse

A Trojan horse virus is so named due to the fact that the actual malicious software is programmed inside of an innocent piece of software, browser toolbar's being one of many techniques. Once the carrier software has installed the virus on the host system the virus will then deliver its payload. Trojan viruses don’t always replicate, they often simply wait for the end-user to initiate an action that allows them to install themselves.


Malware falls into a category of viruses that came about in the first decade of the 21st century with the advent of social networking and daily computer use the harm that could be spread and inflicted through the internet grew at an exponential rate. This prompted malicious coders to create sophisticated programs that would take over your computer flooding systems with ads and other nefarious programs in order to create mayhem. This morphed into another version of malware sometimes referred to as ransom-ware, these sophisticated programs would mimic legitimate anti-virus programs and security programs in an attempt to extort money from the computer user. (Sanders, 2010)

Browser redirects

Browser redirects are malicious code embedded into websites that adjust your internet browsers home page and search defaults to websites that were not selected by the end user, this in turn generates search revenue for the entity responsible for the malicious code.

Malicous software is widely disseminated and the previous threats indicated are just the tip of the iceberg, there are many variants on the previous themes prevalent in the wild. Authors of malicious software often use a variety of techniques that involves multiple categories in order to spread their viruses.

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Michael Reid (author) from Farmington, AR on April 18, 2018:

@bharti, explain what you mean? when you say all names of viruses?

ex: Spectre, Meltdown etc?

If that is the type of names you mean, that would go way beyond the scope of this article.

bharti on April 18, 2018:

pleaase tell about all names of viruses

Brad Masters from Southern California on February 08, 2012:

Great job on describing the distinctions between computer intrusions.

My opinion is that it has been weak programming of the OS that allows the bulk of these viruses to exist.

Many of these poor coding practices began when hardware was very expensive and memory was even more expansive. Coding became limited to the amount of memory available. So many of the protections and checks were not implemented because they either took too much memory or they slowed down the program.

This went on even though processors got extremely fast, and memory got cheaper and more abundant.

The stack overflow failures was a problem that could have been protected by making a range check for the program so that it wouldn't jump into another program causing damage.

There is no reason for a computer to try to divide by zero, yet if the variable or constant is not checked for zero, the divide will cause problems.

These are just a few of the examples of poor coding.

Although UNIX and its derivatives have been successfully attacked by hackers, the basic OS with its protected Kernel is far superior to Windows.

The remote execution feature found in windows is a great feature but it is also a mechanism to be used by hackers.

The pecuniary interest in hacker versus protector might be questioned as an intentional escalation as both sides have a goal. Although their functions are different they both are rewarded for the hack.

Hack is also a term for Cab or Taxi and they have their meters running when you are in it. lol


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