Once the malware, dubbed “Sabpub,” is injected into a user's computer, it has the ability to open a back door that enables miscreants to send commands to the infected computer, including taking screenshots, downloading files or installing additional malware.
Symantec classified the infection as a “very low” risk trojan and research conducted over the weekend by Russian-based Kaspersky Lab may indicate why the threat level is not comparable to that of Flashback.
According to a blog post Saturday by Costin Raiu, director of Kaspersky Lab's global research and analysis team, Sabpub is designed for use in “targeted attacks.”
“At the moment, it is not clear how users get infected with this, but the low number and its back door functionality indicates that it is most likely used in targeted attacks,” he wrote.
Raiu reported that the IP address of the command-and-control (C&C) server which hosts Sabpub is shared with that of a previous attack, known as “Luckycat,” discovered by Kaskersky in March. That was an advanced persistent threat (APT) campaign targeting Tibetan activists.
“The IP address of the C&C to which this bot connects (199.192.152) was also used in other Windows malware samples during 2011, which made us believe we were looking at the same entity behind these attacks,” Raiu wrote.
Further, a separate blog post on Sunday revealed that there are at least two variants of Sabpub in the wild: one which attacks the vulnerability in Java, and another that focuses on an older vulnerability in Microsoft Word for OS X.
“The Word documents exploited a vulnerability in Microsoft Word (including Microsoft Office for Mac), to install an older version of the malware,” wrote Aviv Raff, CTO of Seculert, in an email to SCMagazine.com on Monday. “These seem to be the method of operation used by the attackers before they started using the Java exploits.
Experts suspect that the attacks happened over email, Roel Schouwenberg, senior researcher at Kaspersky Lab, wrote in an email to SCMagazine.com. While the Java vulnerability was likely exploited while browsing websites, the targeted nature of the attacks leads Kaspersky investigators to believe phishing techniques were used as well.
Flashback infected computers through drive-by downloads, which involves nothing more than visiting a bogus web page, thus resulting in greater infection numbers. Although Sabpub used the same Java vulnerability, the malware was spread via targeted spam messages, leading experts like Schouwenberg to say infection numbers could be as low as the double digits.
“People definitely need to make sure their software is up to date, just like with Windows,” Schouwenberg wrote. “So that's not just OS X, but also Java and Office. Obviously, running security software will help.”
A spokesperson for Apple could not be reached for comment.