The Shylock banking Trojan has been revamped with extra features that allow the malware to spread using the chat function of Skype, the popular Voice over IP application.

Shylock can now roam the Skype network thanks to a new propagating plugin called "msg.gsm". This component also adds functionality including the ability to send messages and transfer files using Skype, the ability to bypass Skype warnings and restrictions as well as the facility to clean messages and transfers from Skype history.

Beside the new ability to spread through Skype, Shylock can also spread through local shares and removable drives. Infection by the Trojan allows cybercrooks to steal cookies, inject HTTP into a website, setup VNC (allowing remote control of compromised desktops), and upload files, among other functions.

Shylock is a strain of banking Trojan that first appeared in 2011 and these days is principally targeted at UK banking customers, according to sinkhole data collected by Danish security consultancy CSIS, and illustrated on a map here. "Shylock is one of the most advanced Trojan-banker currently being used in attacks against home banking systems," CSIS warns. "The code is constantly being updated and new features are added regularly."

Microsoft just recently announced that it is discontinuing its Messenger, replacing it with Skype. This may have been a factor spurring the interest of the unknown cybercrooks behind the malware into developing additional components that allow their creation to spread using Skype chat, CSIS speculates.

Previous versions (or configurations) of the malware hijacking live chat sessions in a bid to trick business banking customers into handing over their banking login credentials or into authorising fraudulent transactions. ®

Bootnote

Shylock's moniker is a reference to the inclusion of random excerpts from Shakespeare's The Merchant of Venice in its binaries.