Computer Virus Guide

Virus Prevention

The number of viruses in circulation is growing all the time and so are the methods for transferring them.

When viruses first appeared, the technology in use meant that they were mainly transferred by the exchange of computer discs. Now, they are spread through more diverse routes such as embedded files, e-mails and web pages with active content.

You can minimise your own risk of virus infection with:

The best approach is to use common sense, and the most effective solutions use a combination of the points above.

The following checklists describe some general steps to take to prevent a virus infection:

User Vigilance


  • Keep the office physically secure. Intruders using infected floppy discs have been known to introduce viruses deliberately


  • Do not attempt to open any suspicious e-mails or attachments. Treat as suspicious e-mails from:
    • Anonymous senders
    • Strangers addressing you in a familiar manner
    • Non-standard addresses
  • Be especially wary of any of the above that contain attachments with .EXE, .SCR or VBS file extension names

Malicious programmes can also lurk in more familiar forms. For example, Microsoft Word and Excel attachments can contain macro viruses.

  • Never forward virus warning messages to everyone on an
    e-mail list or contact group. This can spread just as fast and cause as many problems as a virus
  • Never forward funny or joke programmes to others. If you must pass information, send them the URL link and not the programme file itself
  • If you are in any doubt, save suspicious attachments to your local directory, then use virus defence software to examine it in more detail

A simple check is to telephone the alleged sender (if possible) to confirm their identification and credentials.

Virus Defence Software

Basic technical solutions should include the following:

  • Ensure that virus defence software is installed! Virus protection software is readily available from specialist virus protection companies and also from many PC outlets on the high street
  • Ensure that your virus defence software is appropriate.
    Every company has different needs, depending on their technical infrastructure, geographic spread and dependency on technology
  • Use your virus defence software to scan all e-mail attachments before opening them
  • Ensure that your virus defence software has an ‘on access’ function and use it. This type of scanning takes place constantly, automatically checking every file, programme, or document each time it is opened or used
  • Keep your virus defence software up to date
  • Keep your Internet browser up to date by patching it regularly. Most browser updates include new security elements to meet newly identified virus threats. If in doubt, refer to your vendor or their website for advice

Virus Defence Strategy

Technical solutions need to be managed. Define a virus defence strategy for your organisation, addressing:

Alert Services

A number of companies specialising in virus information and/or virus defence software, provide alert services. Alerts are sent by e-mail, whenever there is a new virus outbreak or other Internet security threat.

These companies can prove a good source of information for viruses in general and for specific types of virus.

If alerts are used, they should be combined with a practical procedure for updating the systems at risk, including servers, desktop PCs and Laptop computers.

See our Virus Defence Companies page for some possible sites to check for alert services and subscription terms.

This information based on Crown Copyright 2003
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