Shylock is one of the most advanced Trojans currently being used in attacks against home banking systems. The code is constantly being updated and new features are added regularly.
According to security researchers from CSIS Security Group, the Skype infection is based on a malicious plugin called msg.gsm and allows the malware to send messages and transfer files, clean messages and transfers from Skype history and even bypass the Skype warning for connecting to servers.
Beside the new ability to spread through Skype, Shylock can also spread through local shares and removable drives. Infection by the Trojan allows hackers to steal cookies, inject HTTP into a website, setup VNC and upload files, among other functions.
The program also bypasses the warning and confirmation request that Skype displays when a third-party program tries to connect and interact with the application.
According to a map showing the distribution of Shylock infections that was published by CSIS, there's a high concentration of victims in the UK. However, there are also many Shylock-infected computers throughout mainland Europe and the US.