A new variant of the Warezov strain of malicious code has been discovered by Websense Security Labs.

The new code is currently spreading through the Skype voice over IP network. Although the code itself is not self-propagating, when it runs, a URL is sent to all people in the user's contacts list.

'Skype users receive a message that says "Check up this," with a URL containing a hyperlink,' said a spokeman for Websense.

'When users click on the link, they are redirected to a site that is hosting a file named file_01.exe. If the user runs the file, several other files are downloaded and run.'

The user's contacts also receive the URL within Skype. Once the Trojan is installed in a system, it tries to connect to a Yahoo mail server.

But that server does not seem to be operative and the communication fails. This inoperability is probably an attempt to notify the attacker that a certain machine has been infected.

The downloaded files are other versions of the Warezov malicious code. This code opens backdoors to the users systems and also downloads new code.