Security experts are divided over the effects of the latest rash of worms that exploit a vulnerability in Microsoft's Plug-and-Play software.

There have been 10 malware programs detected that exploit the vulnerability so far. These have caused problems for large corporates and individuals worldwide but Kaspersky, one of the first antivirus vendors to detect the new malware, insists that there is little to worry about.

"There has not been any noticeable increase in network activity that could be ascribed to this worm," said the company in a statement.

"During the Sasser epidemic in May 2004, Sasser caused an increase in network traffic of approximately 20 to 40 per cent. At the moment, there are no signs of a similar increase. This would seem to confirm that, at the moment, there is no epidemic."

But Kaspersky is something of a lone voice calling for calm.

"The Zotob Worm is being underestimated," said network security specialist Arbor Networks.

“We have received calls from a number of large companies that have been devastated by Zotob. Because there have been additional variants of the worm released and the most recent one is through email, this has the potential to become a much bigger problem for companies."

A patch to secure PCs against the new malware has been available from Microsoft since August 9.