This is a big topic and there are a lot of things to discuss within this topic. I think its better I divide this into several parts. So, as this is the first part I’m going to start with “What are Viruses?”
Computer viruses are a fact of modern, internet-connected life. At best, they're annoying performance sucking beasts, but at worst ... kiss your entire data good bye.
We all need to take steps to make sure that our computers are safe, or we risk infection. Complacency is not an option.
And yet, even after all the news, and all the warnings, and after all this time... complacency remains all too common.
Here within this series of posts I have included some information which I help you to understand why anti virus software is a must for your computer and how you can save yourself time, heartache and money....... and well, anti virus software is available online free... so what excuse do you have ? OK. Let’s move.
Computer viruses are self-executing, replicating programs written specifically to change the way a machine works, without the knowledge (or permission) of the operator/owner. Viruses are so called because they behave in a similar way to biological viruses. Just as biological viruses pass from person to person, replicating themselves as they go, computer viruses pass from computer to computer. Unlike most biological viruses, however - computer viruses are entirely man made.
Viruses can impair and seriously damage your computer by, amongst other things; executing random text, audio and video messages, draining memory, deleting files, corrupting programs - even reformatting (or erasing the contents of) your hard disk. At best, the less destructive viruses are annoying and will slow the infected machine up (because of the drain on memory), often resulting in crashes and other unpredictable behavior which can ultimately result in loss of data.
Although a virus needs an infected application to be launched in order to infect other programs or documents, they can hide themselves in your computer (often as innocent files) and replicate (make copies of) themselves until the infected application is launched.
Not all viruses behave in exactly the same way, and not all malicious programs are viruses (like Trojans). Some viruses are only active when the infected application is running, whilst others will stay active in memory until you turn off your computer. However, as the virus is resident in a file or on a disk, exiting the infected application or turning off your computer only removes the virus from memory, it does not remove the virus from the infected file or disk and the virus just lays dormant, until you to reboot your computer and/or access the infected application.
The various forms of computer viruses:
Boot sector viruses infect the boot sector of a hard drive or floppy disk by first overwriting/moving the original boot code and then moving the original code to another sector on the disk, which the virus marks as bad.
File infecting viruses attach/modify any executable files, sometimes replacing the original code with its own code.
Macro viruses are self replicating macros that self replicate and can spread rapidly on a computer and/or network.
Master Boot Record Infectors infect a system's Master Boot Record on hard drives and the Boot Sector on floppy diskettes.
Multi-partite viruses are commonly a combination of techniques of both boot sector viruses and file infecting viruses.
Polymorphic viruses are difficult to detect as they use an encryption algorithm that changes, along with the viruses' appearance, change their appearance with/after each infection.
Stealth viruses hide themselves from a computers' operating system and anti-virus products.
Viruses (including worms) are often distributed via attachments in e-mail spam and, ironically, great deals of e-mail spam (particularly chain letters) are virus hoaxes.
This post is getting bigger and I'm moving to a new post. Will continue discussing about what are Computer viruses, worms and Trojans. And how they behave? on next post.
Click here to read the Part 2 (Computer viruses, worms and Trojans)
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