The technology employed by Sony to protect its music from illegitimate use was picked up by security software as a rootkit which hid files from Windows and made them impossible to detect. But simply using letters '$sys$' in a filename means that any such file will be hidden, even malicious files. And this is exactly what has happened with the latest virus.

Sony says it has 'swiftly provided a patch to all major anti-virus companies and to the general public that guards against precisely the type of virus now said to exist' and that the virus poses no threat when these CDs are played on conventional CD and DVD players. The patch can be downloaded from the Sony website. The effectiveness of this patch has been called into question by the researcher who first discovered the 'rootkit' problem.

'Nonetheless, as a precautionary measure, Sony BMG is temporarily suspending the manufacture of CDs containing First4Internet XCP technology. We also intend to re-examine all aspects of our content protection initiative to be sure that it continues to meet our goals of security and ease of consumer use,' the company said in a statement.

Suspension of production will do little to assuage the outcry provoked by the 'rootkit' storm. 'Fixed' versions of the XCP technology, developed by UK company first4internet, will take some time to reach the commercial CDs on shop shelves, and Sony is now facing lawsuits for its use of the software.

However, it insists it will continue to take steps to protect its property. 'We stand by content protection technology as an important tool to protect our intellectual property rights and those of our artists,' it said.