Oror is a nasty - but, luckily, not widespread - virus which is able to disguise itself in emails containing a wide variety of text and subject lines, making it very hard to spot.

As well as the usual mass-mailing and infection tactics, it also tries to corrupt the operation of anti-virus programs that aren't up to date (but not F-Secure's program). What's more, it also tries to install a backdoor "spy" programme which allows your computer to be remotely monitored over the Internet. Nasty, but with the usual precautions and up-to-date anti-virus software, there's no risk.

* For more information, free downloads and updates, visit www.f-secure.com