Skype users have been warned of a new worm which spreads using the VoIP application's chat function.

The worm, dubbed Skipi by F-Secure and Pykspa by Symantec, arrives in Skype chat boxes as a link to an online Jpeg image. The message urges the recipient to check out the link, but doing so will infect the user's PC.

One of the messages reads: 'Hey, where I put ur photo ;-) now u populr. oops sorry please dont look there. look what crazy photo Tiffany sent me, looks cool.'

Once the link is clicked on the computer is prompted to run or save a .scr file. If this is done the worm enters the system and forwards itself via the Skype application.

"Please note that Skype users only become infected after they have downloaded the link and run the malicious software," said Skype in an advisory.

"The chat message, of which there are several versions, is cleverly written and may appear to be legitimate, which may fool some users into clicking on the link.

"Our security team is actively engaging with domain owners to shut down malicious websites being used to spread the virus."