Software designed to attack damage and destroy computer systems pose a real threat.

A number of Irish companies have been affected by a virus that has begun attacking their computer systems.

The SirCam virus is spread through emails.

Viruses affect computers pretty much the same way they affect people. They make them sick.

The SirCam virus arrives on a computer attached to an email message. The virus is activated when the attachment is opened. Once opened, the virus infects the computer system and sends an email to all contacts in the address book. It also extracts private documents from your computer and sends them on too.

This virus can be difficult to recognise in an inbox as it always contains a different subject line. SirCam also stores itself in the recycle bin and may not be found by anti-virus software. While the message in the email is random, it usually contains the following two lines as the first and last sentences.

Hi! How are you?

See you later. Thanks

It is believed that SirCam first emerged in the United States last week and is now rapidly spreading throughout Europe. Around 30 companies in Ireland have already been affected.

Its design is evidence of the increasing technical sophistication of virus writers.

Conor Flynn of Rits Information Security says this particular virus is very transmissible and is a big threat to large corporations where intellectual property is an asset. There is also the threat that the virus will delete files off workstations on 16 October. Rits Information Security is unsure why that date has been chosen.

The advice to computer users is to update anti-virus software frequently and to avoid opening email attachments without first contacting the sender.

An RTÉ News report broadcast on 24 July 2001. The reporter is Susan Byrne.