Skype is being used by hackers who are infecting Windows PC through integrated "worm" malware.

The Microsoft operated network says users are being duped by instant messages saying "lol is this your new profile pic?"

After clicking the link, a file containing a Trojan horse malware file is download allowing hackers to infect PCs by locking users out of their computers.

"Skype takes the user experience very seriously, particularly when it comes to security," Skype says.

"We are aware of this malicious activity and are working quickly to mitigate its impact.

"We strongly recommend upgrading to the newest Skype version and applying updated security features on your computer.

"Additionally, following links - even when from your contacts - that look strange or are unexpected is not advisable."