Viruses – Types and Examples

If you have read the last article, I assume that you have become familiar with the definition and anatomy of a computer virus. As in medicine, in cases of Computer viruses too we have specialization depending on area of infection and amount of damage. So let us study the basic category of viruses.

Types of viruses

Boot viruses:

These viruses infect floppy disk boot records or master boot records in hard disks. They replace the boot record program (which is responsible for loading the operating system in memory) copying it elsewhere on the disk or overwriting it. Boot viruses load into memory if the computer tries to read the disk while it is booting.
Examples: Form, Disk Killer, Michelangelo, and Stone virus

Program viruses:

These infect executable program files, such as those with extensions like .BIN, .COM, .EXE, .OVL, .DRV (driver) and .SYS (device driver). These programs are loaded in memory during execution, taking the virus with them. The virus becomes active in memory, making copies of itself and infecting files on disk.
Examples: Sunday, Cascade

Multipartite viruses:

A hybrid of Boot and Program viruses. They infect program files and when the infected program is executed, these viruses infect the boot record. When you boot the computer next time the virus from the boot record loads in memory and then starts infecting other program files on disk.
Examples: Invader, Flip, and Tequila

Stealth viruses:

These viruses use certain techniques to avoid detection. They may either redirect the disk head to read another sector instead of the one in which they reside or they may alter the reading of the infected file’s size shown in the directory listing. For instance, the Whale virus adds 9216 bytes to an infected file; then the virus subtracts the same number of bytes (9216) from the size given in the directory.
Examples: Frodo, Joshi, Whale

Polymorphic viruses:

A virus that can encrypt its code in different ways so that it appears differently in each infection. These viruses are more difficult to detect.
Examples: Involuntary, Stimulate, Cascade, Phoenix, Evil, Proud, Virus 101

Macro Viruses:

A macro virus is a new type of computer virus that infects the macros within a document or template. When you open a word processing or spreadsheet document, the macro virus is activated and it infects the Normal template ( general purpose file that stores default document formatting settings. Every document you open refers to the Normal template, and hence gets infected with the macro virus. Since this virus attaches itself to documents, the infection can spread if such documents are opened on other computers.
Examples: DMV, Nuclear, Word Concept.

Active X: 

Java controls and ActiveX will soon be the scourge of computing. Most people do not know how to control there web browser to enable or disable the various functions like playing sound or video and so, by default, leave a nice big hole in the security by allowing applets free run into there machine. There has been a lot of commotion behind this and with the amount of power that JAVA imparts, things from the security angle seem a bit gloom.

These are just few broad categories. There are many more specialized types. But let us not go into that. We are here to learn to protect our self, not write a thesis on computer virus specification.


More by :  Mayur Kamat

Top | Computing

Views: 4542      Comments: 31

Comment need better info

20-Jan-2019 15:21 PM

Comment I really liked it and it is very much helpful to me

25-May-2016 08:08 AM

Comment i like it ...............thanks

ramesh kumar jangti
31-Mar-2016 03:37 AM

Comment I real liked your material....can I be your member?

nwosu chidiebere manasseh [AKA BUSAR]
13-Jan-2016 07:36 AM

Comment As this article is the best of all, I liked it. It helped me to boost,increase and gain my knowledge about computer virus. Thank You Boloji and Mayur Kamat

Chirantan Dey
21-Sep-2015 08:33 AM

Comment The info given by you is really very helpful to the cs Student. As i m doing project in antivirus , can u suggest me that from where i can get datasets of the known viruses.?

09-Apr-2015 04:24 AM

Comment I really appreciates your efforts here, please keep it up and
Please! Please!! Please!!! I want you to recommend an anti-virus software for me

Murtala Ahmed
23-Dec-2014 07:25 AM

Comment this was not particularly helpful, my it teacher says a macro virus isn't real

18-Sep-2014 09:24 AM

Comment This is really helpful and "AMAZING"........ Nice one

Ayandokun Elijah O.
04-Sep-2014 16:02 PM

Comment Content written on types of viruses is really too informative,short and sweet.Really liked it.

29-May-2014 07:45 AM

Comment good you can understand what I want to say

14-Jan-2014 03:04 AM

Comment Good Site.. Very very informative. My son in 5th standard prepared a project after understanding from this site.

Dv buypcantiviruscom
10-Jan-2014 15:04 PM

Comment good one.. provides great help..

11-Oct-2013 09:08 AM

Comment very good

22-Jun-2013 01:47 AM

Comment really good one.....but u didnt write about trojans, worms and logic bombs

12-Jun-2013 14:12 PM

Comment I appreciate ur efforts in makin those write ups available to us. I will like to know about this three types of virus:
Boot sector
Executable file virus
Attack on documents.


Dilinyelu Rose C.B.
26-Feb-2013 07:29 AM

Comment A very wonderful and splendid article,thanks a lot.but we need to also know examples of virus?

Joshua Anugwa
16-Jan-2013 07:15 AM

Comment :)It's nice:D

08-Jan-2013 13:20 PM

Comment This is amazing . Thanks so much for putting this online. tommorow is my test and I was freaking out but now I found something!! Thanks a million!!!!!!

19-Nov-2012 05:48 AM

Comment we realy like it

anna transer
09-Nov-2012 01:11 AM

Comment what about the Rootkit virus?

Aleysha Colinwood
01-Oct-2012 19:42 PM

Comment Is all the type of virus will have if no let me know pls

14-Sep-2012 05:56 AM

Comment Fear not for dying but the dying of faith.

The Dman
13-Jun-2012 11:44 AM

Comment Good, i realy like it

Francis grace
11-Jun-2012 21:19 PM

Comment goood

01-May-2012 07:01 AM

Comment excellent

28-Apr-2012 07:38 AM

Comment i like it is good

karamo bah
26-Mar-2012 12:47 PM

Comment i like it is very good


karamo bah
26-Mar-2012 12:43 PM

Comment i am not clear in obove definition
please send a exact definition types of virus .....

10-Feb-2012 21:58 PM

Comment Yohana: You need to be a member if you want to write and contribute. To just read content of our site, you don't need to be a member.

09-Jun-2011 13:28 PM

Comment Ireal liked your material..can I be your member?

09-Jun-2011 11:50 AM

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