It appears that Skype users are currently under attack from a new worm that spreads via Skype’s chat feature.
The attack comes in the form of an instant message from either an existing contact or an unknown Skype user. To date, several versions of the chat messages have been identified, though the actual contents of it is not relevant.
Suffice to say that even Skype made the admission that they are “cleverly written [to fool]” in the Skype heartbeat blog. While the link appears to be a JPEG photo file, it is in effect a script.
The hapless user who runs it, after being suitably prompted by Windows, will be infected.
An infected computer will then attempt to propagate by sending chat messages to other Skype users.