A virus is the common term used to encapsulate the many forms of malicious software, or "malware" in existence.  These are small computer programs that infect host computers and files.  Some can cause damage to files and data loss; some merely replicate themselves, creating an inconvenience or annoyance.  

Viruses can reside in the code of web pages, come as seemingly benign attachments to an email, or reside on some other media such as a CD.  

Virus Protection

The most effective - but usually impractical - solution against viruses is to isolate a computer system completely from the internet and all external connections or media.  

The industry standard solution is to install "anti-virus" software on every machine.  This software runs in the background, quietly scanning every email, every document, every web page and every file opened on a PC.  

There are thousands of viruses and new ones are discovered every month. Therefore, the virus definitions used by anti-virus software must be kept updated on a regular basis.  Fortunately, modern anti-virus software can handle this updating seamlessly over the internet. It is vitally important for the health of your PC to keep your anti-virus software up to date.


Additional protection can be afforded through the use of a firewall.  A firewall acts as a gateway between your PC (or network) and the internet. In simple terms, a firewall monitors all messages to and from the PC, noting the source and destination of each message.  Firewalls can be told which programs are allowed have internet access (for example, a web browser) and which are not allowed (perhaps a text editor).

There are thousands of viruses and new ones are discovered every month.

If a program requests access, you can be alerted to approve or deny the access.  In this way you can control exactly which programs can access the internet.  It may seem a little daunting when messages appear with seemingly inexplicable file names claiming that they need internet access, but with a little due diligence and patience the firewall can be trained to only allow the legitimate programs to access the internet.

Firewalls also block attempts at intrusion from external sources.  


Content Filters

Content filters are used by some organisations in their email system.  When an email comes into the organisation's email server (or their IT provider's server) the email is often scanned to see if any attachment is of a banned type.  The email server will have a list of banned file types and any disallowed file will be deleted.  At this time the message will also be scanned for viruses and 'spam.'

Good practice - Tips for virus avoidance.

  1. Be wary of emails from unfamiliar senders.
  2. Do not open an email attachment from an unknown source.
  3. Familiarise yourself with the common file extensions (i.e. the last three letters in a file name, such as .doc, .xls, .pdf, etc.).  Do not open an attachment unless you are satisfied that you know what type of file it is.  
  4.  Beware .exe files!
  5. Do not download and run files from the internet without scanning them for viruses first, and satisfying yourself that they come from a trustworthy source.
  6. Always keep your anti virus software up to date!


Sometimes a warning email is circulated, heralding the arrival of a vicious new virus.  Such warnings should be verified by looking at an authoritative source, such as one of the big anti-virus companies before any action is taken.  There are many websites whose sole raison d'etre is to debunk hoax virus warnings.  

Of course, these hoaxes prey upon our fear of viruses, encouraging us to forward the message to everybody in our address book: which is a pretty effective virus, if you think about it!