Another Trojan horse is spreading through the Internet telephone network of Skype Ltd.

The malicious code, known as both Warezov and Stration, is similar to an earlier version detected in February, but with a new URL (uniform resource locator) and a new version of the malicious code, according to an alert posted Thursday by Websense Inc.

Websense warns Skype users to watch for the message "Check up this," with a URL containing a hyperlink.

The code itself isn't self-propogating but when it runs, the URL is sent to everyone on the user's contact list.

When users click on the link, they are redirected to a site that is hosting a file named file_01.exe. Users are then prompted to run the file and if they do, several other files are downloaded and run. The downloaded files are other versions of the Waresov/Stration malicious code.

Once the Trojan is installed in a system, it tries to connect to a Yahoo Inc. mail server to send an SMTP (Simple Mail Transfer Protocol) message.

However, that server doesn't appear to be operating, according to Websense.

Skype, a division of eBay Inc., offers a number of Internet-based services, including VOIP (voice over Internet Protocol) and instant messaging.