As Skype becomes a vital piece within Microsoft software, the amount of malware targeted at the Internet telephony platform will surely rise, opening up new avenues for infecting corporate PCs.
The trend has already begun, with reports last week that the Shylock home-banking malware had been updated with new Skype-related functionality. The addition came in the form of a plug-in that allowed the malware to send rogue messages and files and to connect with applications on the Web without triggering a warning and confirmation request from Skype.
Since the Shylock discovery by CSIS Security Group, Trend Micro has found related malware, which the security vendor calls "worm_phorpiex.jz." The malware acts similarly to Shylock. It can send messages containing attachments that are actually copies of itsself and can connect to an outside server to download malware and execute it on the host computer.
Nearly 84% of the infected computers today are in Japan, with roughly 2% in the U.S., Trend Micro said.
Microsoft said it was aware of the new Skype threats. "We are currently helping protect customers by blocking the malware known as Shylock, Phorpiex and Bublik," the company said in an emailed statement. "We continue to encourage customers to avoid opening links from untrusted sources and visiting untrusted sites." (Bublik and Shylock are alternate names for the same malware.)
[See also: Is Skype safe for business?]
Malicious software is not new to Skype. Last year, security researchers found that instant messages sent to Skype users contained links that led to a variant of the Dorkbot malware. The malicious app could take control of a PC, steal information and use the system in launching distributed denial-of-service attacks.
Other security flaws have been found in Skype over the years, but what's different today is how the application is becoming a bigger part of Microsoft's product portfolio. In March, Microsoft, which paid $8.5 billion for Skype in 2010, plans to retire its Messenger instant messaging (IM) service and ask users to switch to Skype, which includes an IM platform.
Microsoft has also launched a Skype-centered hub for small business and is working on integrating Skype into its corporate enterprise and collaboration products, including SharePoint and Office.
For cybercriminals, this opens up many more options for infecting a PC through Skype, said Jamz Yaneza, a threat research manager for Trend Micro. "As technologies become more public and their usage becomes more rampant, we often see an increase in attacks," Yaneza said.
Skype features sure to entice cybercriminals include its connections for third-party plugins, which Shylock exploits. In addition, the software includes a Web browser, which is a favorite target for hackers. On the PC, Firefox and Microsoft Internet Explorer are constantly under attack.
Companies can reduce their exposure by restricting employees to Skype Premium and installing the business version as soon as Microsoft releases one. The free consumer version is more vulnerable to attackers, because it does not have the same controls available to corporate IT departments, Yaneza said. In addition, companies should restrict plugins to only those approved in advance.