First CSIS researchers unearthed a campaign misusing Skype to replicate and spread the Shylock banking Trojan with a plugin called msg.gsm that, when it was first spotted five days ago, was detected by none of the AV solutions used by VirusTotal.
Then this week Trend Micro researchers discovered highly dangerous worms also being propagated via Skype messages containing malicious links.
The Bublik worm propagates further on via removable drives, and is capable of dropping other malware onto the infected computer (which he does) and of executing commands from a remote malicious user. It also has rootkit capabilities, which make it extremely difficult to detect.
The Phorpiex worm drops copies of itself in all removable drives, connects to specific IRC servers, download other malware and sends copies of itself as attachments in email messages.
Among the malware it downloads is also a plugin that creates the malicious Skype messages that aid its diffusion to other victims' computers.
With the announcement of Skype in the Workspace and the reported upcoming shut down of Windows Messenger, first-time Skype users and businesses should be careful when using Skype and refrain from following links in random messages.