Researchers with Malwarebytes have observed a new variant of Tinba banking malware being distributed via the HanJuan Exploit Kit as part of a malvertising attack that involves advertising and URL shortening service Adf.ly.
Jerome Segura, senior security researcher with Malwarebytes, told SCMagazine.com in a Thursday email correspondence that the majority of infections have been observed in the Netherlands, but he added that the campaign is still in its early stages and could expand.
The threat was made possible because the attackers were able to successfully submit a malicious advertisement to Adf.ly, which was then arbitrarily displayed to users who clicked on shortened Adf.ly links around the web.
“Adf.ly monetizes its service by displaying ads when people click on the shortened link,” Segura said. “Before the shortened link redirects to the actual URL, an ad is displayed for a few seconds. This is where the malvertising happened.”
Once the malvertisement was displayed, a redirection chain triggered without any user interaction, Segura explained. According to a Wednesday post, users were ultimately taken to a compromised Joomla website that pushed what is believed to be the HanJuan Exploit Kit.
Researchers observed the HanJuan Exploit Kit targeting two exploits in order to deliver the Tinba variant – an Adobe Flash Player vulnerability, CVE-2015-0359, and an Internet Explorer vulnerability, CVE-2014-1776, the post said.
The Tinba variant, which was initially identified by Malwarebytes as ‘Fobber,’ was observed going after sensitive information – including Google, Microsoft, Facebook and Twitter credentials – by hooking browsers and grabbing usernames and passwords before they were encrypted, the post said, adding the malware was not observed stealing banking credentials.
“This is an evolved version of Tinba v2, which was identified by security researchers at Fox-IT,” Segura said. “While the core of the program is more or less the same, the authors of this piece of banking malware have improved its encryption capabilities, making it harder for security researchers to properly identify and take down.”
To address these types of threats, Segura said that advertising networks must ensure they are delivering clean content, and end users must make certain their computers are fully patched and are protected with adequate security solutions.