A hacker's backdoor affects an estimated million Vaio notebook computers, manufacturer Sony warns.

The security flaw could let crackers manipulate or delete data on hard disks and is found in proprietary software installed on Vaios sold in Asia, the Middle East and South Africa since May 2001.

Vaio models bought in Europe or America are believed to be immune to the problem, which relates to Manual CyberSupport for Vaio Version 3.0 and Version 3.1 that is pre-installed in some models of Vaio computers and the Recovery CD.

In a statement , Sony said because of the vulnerability "there is a danger that a third party may find a way to by pass the software's security and access the Vaio through a homepage on the Internet or by email without authorization."

Either an "Internet homepage, email containing HTML or a HTML file attached to an Email" containing malicious code might be used to exploit the glitch.

"If the Vaio is attacked in this way, it may result in stored data being over written, erased or copied. In this instance, running regular anti-virus software will not protect the affected models of Vaio", Sony warns.

Sony has provided a software patch on its site and is notifying Japanese customers, where the majority of affected laptops were purchased, by email. A call centre to field calls on the problem and offer affected customers the software fix on a CD, has also been set up.

Sony estimates the software bug will cost it up to $1.49 million to fix. ®