Shylock, a trojan dropper that steals bank account information, is employing a new trick to avoid detection: hiding from researchers who may be studying it via remote desktop connections.
Initially discovered in February 2011 by security firm Trusteer, Shylock delivers web injects into victims' browsers and logs keystrokes.The malware is concealed in endpoint device memory files and rewrites Windows processes. Shylock, named after the ruthless money lender in Shakespeare's The Merchant of Venice, also deletes its installation files, runs solely in memory, and begins the process again once the infected machine reboots.
George Tubin, senior security strategist at Trusteer, told SCMagazine.com on Wednesday that Shylock appears to be a widespread threat largely undiscovered by victims, as it sits idly on their computers until they visit targeted banking sites. Victims mostly are customers of U.S. and European financial institutions, he said, and the attacks are often initiated by phishing emails or drive-by downloads.
“This is good, general purpose financial malware that we see along with Zeus, SpyEye and a host of other malware families that target these institutions,” Tubin said. “Fraudsters are trying to get onto user devices, the weakest link, to penetrate the corporate network.”
The latest variant of Shylock is now able to detect remote desktop connections, a preferred method of analyzing malware in lieu of researchers needing to access physical machines within a security operations center, Tubin added. Trusteer has seen malware use other evasion strategies on virtual environments, like network scanning tools or sandboxing mechanisms, but never specific coding that eludes remote desktop software.
“This is the first time we've seen this in malware,” he said. “We do see malware doing more things to avoid so-called virtual environments. For instance, sometimes malware has a sleep function, so once it gets in, it won't start for a time. We see an increasing trend in malware being able to evade virtual environments.”
Vikram Thakur, principle security response manager at Symantec, emailed SCMagazine.com on Wednesday, and shared other techniques used by malware to evade virtual environments, including monitoring mouse movement.
"At the end of the day, malware authors realize that organizations use automated techniques in order to determine the capabilities of malware,” Thakur said. “By investing development time to circumvent sandboxes, they are trying to buy themselves some time before they get detected."
Safeguards against advanced threats with multiple evasion methods in place include use of contextual application software or real-time detection technology, Trusteer advised.