by Kim Evans

Created on: January 18, 2005   Last Updated: April 19, 2007

Computer "Virus" share some of the traits of their biological counterparts (hence why they are named "Virus") and if you understand how a biological virus works, you start to get an idea on how a computer virus works.

A biological virus passes from person to person, very much the same way a computer virus passes from computer to computer. The infection is also normally initiated through contact with an infected host.

The biological virus is not a living organism, but instead, a fragment of DNA within a protective "casing". It has no way of reproducing or doing much of anything else by itself. It becomes active by introducing itself into a living cell within our body. The DNA then uses the cell's existing generics to reproduce itself, sometimes filling the cell to bursting point and spreading further viral elements, or in other occassions, viral bits bud off from the cell one at a time, keeping the cell alive.

A computer virus is very similar. They are harmless when they first arrive on your computer. It must use the execution of another program or file to enable it to be activated. Once it has been activated, it can then infect other programs and files.

There are literally thousands of viruses that can be transmited to your computer via LANs, Internet connections and disk swaps. Computer viruses are normally variants of the following classifications:

MACRO VIRUSES
Macro Viruses use commands (or "macros") embedded in other software to infect, and spread to, other files viewed by that software. Macro viruses are also platform independant. That is to say, the virus can pass between DOS, Windows and MAC systems, as long as the system has the application installed that the macro virus was written under (i.e. Microsoft Word).

WORMS
Worms duplicate themselves and use communication programs such as email to spread. They can look at contacts within your email address book and send themselves to contacts listed within.

FILE VIRUSES
File viruses attach themselves to other software. When the software is executed, the virus first loads itself into memory so that in can further infect other files or begin damaging your computer.

TROJAN HORSES
Trojan Horses are programs that claim to perform a particular function, but really, do something completely different. This can involve infecting your computer with a virus or erasing files, or in the worst case senario, erasing the hard-drive completely.

BACKDOOR TROJANS
These are programs that allow third-party users (also known as Hackers) to remotely control your computer via a LAN or via the Internet.

BOOT SECTOR VIRUSES
These are no longer so common. They would infect a computer's startup program so that the virus would become active as soon as the computer booted up.

If you want to find out more about the different types of viruses, there is a lot of information readily available on the Internet. There is also a lot of information with regards hoax viruses.

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