How Viruses Work By- Paul D Kennedy

The source of this article at the bottom And Profile of the writer

A virus is a small piece of software or computer code that is inserted by a rogue programmer in a legitimate program, such as a spreadsheet. The code has the ability to replicate itself, hide, watch for a specific event, and deliver a payload. The payload can be just a prank or, more likely, destructive.

How viruses work

When a virus first enters your computer, there are several places where it can end up.

Boot record viruses target your computer's master boot record. The boot record is the first part of the operating system (which controls how everything works on your computer) that the computer loads when it is started. The computer must read this record to find out how the disk is organized before it can begin loading all the files needed to operate the computer. By putting its code in the boot record, a virus can guarantee it's executed... even before the operating system is loaded.

Program viruses look for executable files, such as files that end in.exe. It usually inserts itself immediately behind the program's header, a small section of code at the start of a file that contains information about the file. By inserting itself behind the header, the virus can ensure that when the legitimate (but infected) program is run the virus is executed first.

Replication

Usually the first thing a virus does is to insert copies of itself into other program files. Each of these copies replicates itself in turn whenever its program file or host is read by the computer.

Camouflage

Many viruses disguise themselves in order to avoid detection by anti-virus software. There are various ways in which a virus may do this.

It may, for example, insert fake non-functioning bits of code inside the working sections of the virus code. Then, each time the virus replicates, it changes the fake code.

In this way the virus can disguise its identifying signature, the particular sequence of commands in the code which allow it to be recognised. In other words, once the virus has replicated the new copy will look different than the original copy.

Here's another way a virus can disguise itself.

The file header of any program will contain details of the exact length of the file. Adding the virus code to the program will increase its length and the changed length is liable to discovery. A virus may falsify the information in the header about the length of the file so that the program file seems to be the correct size.

Event checking

Each time a virus runs it checks for a specific condition or triggering event. If the condition is not present, the virus does nothing. But if the triggering event exists, the virus delivers its payload.

The triggering event is usually a particular date. As the virus will already have replicated itself thousands, perhaps millions, of times, the payload will be delivered in hundreds of computers all at the same time for a grand effect.

Some viruses, alternatively, dump their payloads after they have replicated themselves. Others are programmed to go off after a certain length of time has passed.

Payload delivery

The payload a virus delivers may be, if you are extra lucky, quite harmless... nothing more than a rather rude or crude message. More likely, however, the payload will be highly destructive.

Viruses can erase or scramble files, which causes you to lose data and programs. They can destroy the information on your hard drive that tells the operating system how to find files on the disk and thereby stop your computer from working.

The most insidious viruses are the ones that quietly insert themselves into files and then do things such as stealing passwords or subtly changing numbers at random in an accounting application.

Memory-resident viruses

Some viruses can load themselves into memory so they can keep running in the background as long as the computer remains on. This gives viruses a much more effective way to replicate themselves.

In addition, viruses resident in your computer's memory can be on the look-out for attempts by anti-virus software to find infected files and can return phoney information to hide itself from detection.

Safe computing

Internet viruses are a plague. But they are not as bad as they were only a few years ago as firewalls and anti-virus software are now being used almost universally. These now block viruses before they enter your computer with a high degree of success.

You can protect yourself with a modicum of common sense:

1-Install anti-virus software

2-Ensure your anti-virus software is up to date

3-Be highly cautious when opening emails or downloading material from the internet

Paul Kennedy is the marketing manager of Jupiter Support (Ireland). He can be contacted by email to paul@jupitersupport.ie. You can also go to jupitersupport.ie where you can use chat or Skype to talk with a technician free of charge. Alternatively you can call 0766803006 to speak to a technician and get free advice. Jupiter Support only charges a fixed fee of€19.99 to rid your computer of any and all viruses on a no-fix/no-fee basis.

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