New virus attacks PCs

A new virus which can infect PCs as soon as they connect to the Internet has hit up to 18million computers worldwide.

The worm, called Sasser, is set to cause problems as users return to work today after the bank holiday.

Small and medium-size businesses which do not have advanced antivirus software are most at risk, experts warned.

Graham Cluley, of anti-virus firm Sophos, said: 'You can get it just by connecting to the Internet, you don't have to open an e-mail or go to a dodgy website. If you don't have a firewall in place there is a good chance you will be hit.'

Sasser attacks recent versions of Microsoft Windows, such as 2000, Server 2003 and XP, and causes computers to slow down and crash.

In Australia, 300,000 passengers were stranded on platforms when the virus prevented train drivers talking to controllers in New South Wales.

A spokesman for Microsoft UK said: 'With the bank holiday, we won't know the scale of the damage, if any, until today.'

The more Internet users surf the Web, the more they are likely to get the virus because it lurks on a number of sites.

Mikko Hyppoenen, of Net security company F-Secure, said: 'There are always going to be security holes in mainstream products. Even if these are not made public, the bad boys will find out about them anyway.'

A security patch to protect PCs from the virus can be downloaded from Microsoft's website.