Skype, the internet communications platform, is being used by hackers to distribute a "worm" that infects Windows PCs.

When users click on an instant message saying "lol is this your new profile pic?" they unwittingly download a file containing a Trojan horse malware file.

This opens a backdoor allowing hackers to hijack infected PCs and recruit them into a "botnet army".

Users can be locked out of their machines and held to ransom.

According to internet security specialist Sophos, the worm is a variant of the well-known "Dorkbot" worm which has been spread by social media platforms such as Facebook and Twitter.

When the worm infects a computer it sends out the "lol" message to the user's contact list.

Unsuspecting recipients think the message has originated from someone they know and click on the link, thereby downloading the malware payload.

BBC News