Researchers at security firm Volexity noticed that the website of a media organization based in the country of Georgia had been serving a new version of an old Mac Trojan to specific visitors.
According to experts, the compromised news website has English, Russian and Georgian sections, but only the Georgian language pages appeared to deliver the malware. The threat is a new version of OSX/Leverage, a backdoor first spotted back in 2013.
Interestingly, not all visitors were targeted. JavaScript code planted on the site profiled each user and only served the malware if certain conditions were met. The malware was pushed only to devices whose user agent showed that the victim accessed the site from a Mac and a web browser other than Chrome.
The script also checked cookies to determine if the user had previously visited the website and analyzed the malicious JavaScript code. If a returning user is detected, the exploitation chain is terminated.
If all the conditions are met and the potential victim is using the Safari browser from a Mac computer, an iframe is loaded and a fake Adobe website is displayed. The site is designed to trick users into downloading a fake Flash Player critical update.
The malicious Flash Player update is delivered via a Metasploit module that abuses Safari functionality to force the download and execution of an OS X application. However, the victim still needs to allow the execution of the file when prompted or manually execute it from the Downloads folder.
Once executed, the malware creates a Launch Agent for persistence and opens the genuine Adobe Flash Player website to avoid raising suspicion. The backdoor contacts its command and control (C&C) server and sends it information about the infected system.
“Unlike the earlier version of the malware, this new version does not limit itself to a predefined set of commands and instead allows an unrestricted command shell capability back into an infected system,” Volexity researchers said in a blog post.
The new version of the Leverage malware, which was also spotted by Sophos earlier this month, is signed with an Apple code signing certificate issued to a developer apparently named “Aleks Papandopulo.”
The first version of Leverage had been disguised as an image file and in some cases it downloaded a logo of the Syrian Electronic Army hacker group onto compromised machines.
Interestingly, Volexity has discovered a link between an IP address associated with one of the domains serving the new version of Leverage and Stantinko, a recently uncovered botnet that has powered a massive adware campaign since 2012. The Stantinko operation has mainly targeted Russia and Ukraine.
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