Introduction

A computer virus is rather like a biological virus in that it spreads through contact with others; not through sneezing or the like, but across networks, especially the Internet, and most commonly transported by E-mail. None of what follows is scaremongering. It can and does happen, all the time, all over the world. It is a major headache for computer and network managers to prevent infection in the first place and to clean up infected machines after the event. It also generates lots of network traffic that slows down legitimate communications.

Usually a virus arrives as an attachment to an e-mail with a subject line like "That document you wanted", but be warned, there are a great many variations on this theme. It may even appear to come from someone you know. This is known as "spoofing" and will be explained a little later. The attachment is not what it seems, and when you attempt to open it a program is run that infects your computer. It may appear as if nothing has happened. However, most viruses' first action is to search for e-mail address books so that it can e-mail itself to everyone on the list. It will pick your address, or one randomly from the list, as the "spoof" so recipients will think it has come from you and be more trusting of it.

The virus may be more malignant. It could corrupt files or even render your computer unbootable. Another possibility is that it installs a Trojan Horse. Such a device allows others access to your computer. They can connect at any time, read your files, discover your passwords, view what you are typing on the keyboard etc. Some viruses contain their own e-mail server so that spammers can use your machine to distribute their Spam.

Many viruses exploit bugs in the Operating System or Application Software you are using. And because the vast majority of desktop PCs are running Microsoft products, they get the lion's share of the blame. This is not entirely unjustified. There is barely a week that goes by without another bug being discovered. Microsoft have been guilty of ignoring warnings in the past, and take a long time to issue corrections (called patches) even now. A common view is that Microsoft should have written the software properly in the first place. Windows XP, supposedly the most secure operating system Microsoft has ever released, has still had serious security warnings and a number of patches after it was released.

If you do need to reinstall Windows, be sure to reinstall all the earlier patches that were used to close previous faults with the system. News about newly-discovered viruses may be found on some of the links at the right-hand side of this page. They are likely to appear there before Microsoft admits to them and releases a patch, but a useful page is currently Here.

AntiVirus Software

You are strongly urged to install AntiVirus software on each computer that you have. Norton AntiVirus and McAfee virusscan are two popular products, but there are many more on the market. The best products are those that regularly download new virus signatures so that newly-detected viruses may be identified and dealt with properly. The software should be configured to do this on a daily basis. The products are available in most computer shops and on the web. You are advised to shop around to obtain the best prices. Each purchase usually comes with a years' subscription and must be renewed thereafter. It may seem a little unfair, but it allows the companies to continually improve their products and provide you with the latest protection.

Firewall

Some malicious programs can find their way into your computer without the use of e-mail. Briefly, a firewall monitors attempts to connect to your computer and checks whether or not they could be malicious. Positive identification means the attempt is blocked. Some parts of your computer are particularly vulnerable and should be protected from the Internet. For a comprehensive explanation visit Firewalls.

Patches

A patch is a piece of software or program that is designed to correct a bug in another piece of software. The patch alters the program so that the bug is corrected. In an ideal world this is not a problem. However, since a patch is itself a program, it too may have a bug and not work correctly. It is important to make a Backup of your important data, and preferably the entire system, before the patch is applied. It is not unknown that users have had to go back to square one and reinstall Windows when a patch has gone wrong.

Microsoft Internet Explorer

ActiveX is a Microsoft technology that allows programs to be run in a web browser. The programs are written in sophisticated programming languages and can do many useful things. Unfortunately they can do many bad things as well, including stealing your data, deleting it or destroying your system. By allowing your web browser to download programs from untrusted websites without knowing what they might do, you place yourself at risk.

The following settings will help to make your computer as safe as possible. The window is found by selecting Tools -> Internet Options then clicking on the Security tab and then the Custom Level button. Unfortunately, ActiveX is favoured by Microsoft and you must therefore endure a dialog box warning you that ActiveX controls have been disabled, each and every time one is encountered. There is no way to turn this warning off.

• ActiveX controls and plug-ins
  • Download signed ActiveX controls: Disable
  • Run ActiveX controls and plug-ins: Disable
  • Script ActiveX controls marked safe for scripting: Disable
• Downloads
  • Font Download: Disable
• Microsoft VM
  • Java permissions: Disable Java
• Miscellaneous
  • Allow META REFRESH: Disable
  • Display mixed content: Disable
  • Drag and drop or copy and paste files: Disable
  • Installation of desktop items: Disable
  • Launching programs and files in an IFRAME: Disable
  • Navigate sub-frames across different domains: Disable
  • Software channel permissions: High Safety
  • Userdata persistence: Disable
• Scripting
  • Active scripting: Disable
  • Allow paste operations via script: Disable
  • Scripting of Java applets: Disable
• User Authentication
  • Automatic logon with current username and password