VoIP operator Skype is warning users about a new Windows worm spreading through the company's chat message service. According to Skype's Heartbeat blog, the attack appears as a chat message from a friend asking them to click on what appears to be a link to a JPEG image, but actually points to the virus file.

Clicking on the link will prompt Windows to ask for permission to run a .scr file, used for screen savers. If granted, the malware - known variously as Skipi, Pykspa and Ramex - will first attempt to disables access to security-related websites by modifying the hosts file, and then it installs another data-stealing piece of malware.

Skype said it is working with leading antivirus vendors, and encourages all its Windows users to update their antivirus software to make sure they have the latest protection. For more experienced users – who probably won’t click on the link in the first place – manual instructions for removing the worm are also available.