Experts are warning of a new piece of malware spreading via the Skype VoIP application.

The Trojan is a variant of the Warezov/Stration code which arrived at the end of last month.

Skype users receive a message from a contact suggesting they check out a URL. When the page is visited they are asked to download and install a file containing the Trojan.

"Once the Trojan is installed in a system, it tries to connect to a Yahoo mail server to send an SMTP message," said web monitoring firm Websense.

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

The Trojan also accesses the user's Skype account and sends a similar message to all contacts. The code does not install any vulnerability in the Skype code itself.