Microsoft have admitted that their e-mail programmes cannot handle birthday data in electronic cards without leaving a way open for viruses.

All that is needed is for a piece of code to be placed in the data of the birthday field of the card and then send it to the e-mail victim. As soon as the card was opened by Outlook 97 or 2000 or Outlook Express 5.01 or 5.5, then this could could crash the application.

This code can only be triggered if attachments are opened, it cannot be made to open these attachments automatically. By opening an e-mail alone will not trigger the virus. When the attachment is double-clicked or dragging it into the contacts folder is the only way of setting off the trap.

Microsoft have recommended that those people using Outlook or Outlook Express download a patch from their website. A fix will be included in Service Pack 2 for Internet Explorer 5.01 and 5.5 and also in Windows 2000 SP2.