What are computerviruses?

The oldest kind of computerviruses are small computerprograms that attached themselfs to other normal programs and were loaded into the memory when that program started. A virus could also place itself onto the bootsector part of a disk (a so called bootsector virus) and was loaded into the memory when a computer booted from an infected disk.

There are also some newer viruses which use special functions in programs that are already installed on your computer. These viruses are mostly called 'macroviruses' because they make use of the macro function in other programs. Macroviruses that make use of the macrofunction in Microsoft Word are very wide spread.

But there are also viruses that make use of the many faults in the operating system itself. There are for example many viruses that make use of the features (faults) in the e-mail program 'Outlook Express' written by Microsoft.

But even if your not using e-mail are unknow programs your computer could be infected by a virus, to be exact a wormvirus. A wormvirus is a virus that spreads through a network by searching the network with well known technics. If it finds a computer which has security leaks in it it will infect this computer and the process starts again.

The formentioned effects of a virus would not be that bad was it not that the virus almost always has some destructive payload inside itself. This 'payload'can be deleting files, erasing small portions of a file or even adding some bytes to a file every time that file is opened. Information is lost in this way or the harddisk is getting full. There are also virusses that destroy the file allocation table causing the harddisk to become unreadable. It can even be worse the harddisk gets formatted. An effect which is not harmfull to the data on your computer is that some computervirusses use infected computers to launch an attack on a website. This is done with masses of computers at the same time. The website pages are requested in such a high rate the the server on which the website resides gives up a produces errors.

Recognizable effects

After reading the text above you can create a couple of point with which you can check if your computer is infected by a computervirus. These point could be:

-Disappearance of files.
-Files are getting larger or smaller without any reason.
-The time/date mark of a file is changed.
-Programs are getting slower or are acting strange.
-The whole computer is getting slower.
-Appearance of messages/warnings on the screen.
-A write protected disk can't be read but a non-write protected disk can be read.
-Parts of the hardware doen't work normal.
-Persons in your addressbook receive mail from you, but you haven't send it yourself. F.Y.I. the receipt of a virus from a specific address does not mean that the computer if the owner of that address is infected. Virusses can produces fake addresses and send a copy of itself with the fake address as a return address. It can produces these addresse out of the addressbook on the infected computer.

Protection is better than healing!

To prevent your computer of becoming infected with a computervirus you could use the following rules.

1) Never start an unknown program, first check it with your virus scanner.
2) Don't use programs from an unknown source.
3) Don't open e-mail from strange senders and don't open attachments in these e-mails.
4) If you don't have to write on a diskette, write-protect it if you putt it into another computer.
5) Always virus check a diskette before opening a file.
6) Be sure your computer has the latest security updates.
7) Install a firewall on your computer to prevent infection by a wormvirus.

And the important thing of all:

8) Use an antivirus program which is up to date.

Anti-virusprograms

An anti-virusprogram is a computer program which is able to check files for computer virusses. Mostly it comes in 3 different forms, these 3 forms can be 3 different programs but it also can be 1 program which has the 3 functions combined.

The first form is a program which scans the computer memory during startup. In this way you avoid starting your computer with a virus in the memory. If the scanner gives a warning it means that the bootsector or the bootfiles are infected.

The second form is a program with which you can scan your computer manually for virusses. This means that you can order the program to check all files on the hard disk, or another disk, for virusses. This should be done periodically.

The third form is a memory-resident virsusscanner. The program is started and stays in memory. The program scans every file that is opened for virusses. Futher it scans every received e-mail before it can be opened.

If a virus is found it can often be removed from that the infected file, if not it is better to delete the infected file than to save it. If it is a program file this means you have to reinstall the program.

Good anti-virusprograms which can be kept up-to-date easilly are for example McAfee, Norton Antivirus en Norman. A trail version of these programs can be downloaded from the site of the creators.

A trail version of Norton Antivirus can be downloaded on this page.

A trail version of Norman Viruscontrol can be downloaded on this page.

Updates for anti-virusprograms

Because there are discovered many different new virusses every week, it is neccesary to renew the virusdefenitions regularly. These new definitions can be downloaded on the website of the maker of the program itself.

McAfee for example distributes new definitions weekly. And because this ever growing number of virusses demand for improvements of the program itself there are also improvements for the program to be downloaded. These improvements help to discover a virus more easily and a virus can be removed from the files more easily.

After a new installation of McAfee it is wise to download to both download the new virus-definitions as well as an update for the scansystem itself. Which update should be downlaoded can be told in the following way:
After McAfee is installed en started a 'weaponshield' appears in the system tray, by right clicking and choosing 'ABOUT' you can get the version number of both virusdefinition and scanengine. After comparing these version numbers with the ones below you should get an idea what to download.

Norton Antivirus

The update for Norton Antivirus distributed on can be downloaded here.

Protection against viruses