Security Experts:

Microsoft Downplays Impact of "Fireball" Malware

The Fireball malware detailed early this month might not have had as much impact as originally reported, Microsoft claims.

Operated by Chinese digital marketing agency Rafotech, the Fireball malware was designed to take over targeted browsers, spy on victims, and run code on compromised machines. Because of that, the threat can be used to download additional malware onto an infected machine, and also allows its operators to manipulate the victim’s Internet traffic to generate ad revenue.

The malware was discovered by security firm Check Point, which suggested at the time that over 250 million computers worldwide had been affected by the threat. Furthermore, the company also said that Fireball impacted 20% of all corporate networks out there.

According to Microsoft, however, the initial report on Fireball might have exaggerated the malware’s reach. The company also claims that it has been tracking Fireball since 2015, meaning that it isn’t as new as previously suggested.

“Our teams knew differently because we have been tracking this threat since 2015. While the threat is real, the reported magnitude of its reach might have been overblown,” Hamish O’Dea, Windows Defender Research, says.

The researcher reveals that the initial Fireball infection comes through software bundling, as the malware is installed alongside other programs users download via their browsers, often “apps or media of dubious origin (pirated apps, games, music or video, cracks or keygens, etc.).”

The Fireball suite also includes clean programs, and the malware abuses these apps as host processes to load malicious code and evade behavior-based detection. The suite’s components were designed to “either persist on an infected machine, monetize via advertising, or hijack browser search and home page settings,” O’Dea says.

Microsoft’s researcher confirms the malware was designed to hijack the browser’s home page and default search settings, thus loading a search page that earns malware creators revenue from users’ searches.

The tech giant reveals that the most prevalent malware families in the Fireball suite are SupTab, Xadupi, Ghokswa, and Sasquor.

According to Microsoft, Check Point erroneously estimated Fireball’s spread because it relied on the number of visits to the search pages (some visits came from clean machines) and on analyzing Alexa ranking data.

“The estimates were made from analyzing Alexa ranking data, which are estimates of visitor numbers based on a small percentage of Internet users. Alexa’s estimates are based on normal web browsing. They are not the kind of traffic produced by malware infections, like the Fireball threats, which only target Google Chrome and Mozilla Firefox. The Alexa traffic estimates for the Fireball domains, for example, differ from Alexa competitor SimilarWeb,” O’Dea points out.

Based on “intelligence gathered from 300 million Windows Defender AV clients since 2015, plus monthly scans by the MSRT on over 500 million machines since October 2016,” Microsoft determines that the scale of the Fireball threat over time was much lower than Check Point suggested.

Specifically, the company says Malicious Software Removal Tool (MSRT) encountered SupTab 4,920,456 times, Xadupi 3,373,023 times, Ghokswa 1,503,968 times, and Saquor 1,287,297 times.

Microsoft added the Fireball family of malware to its MSRT over the course of three releases in September 2016, October 2016, and February 2017. Thus, the number of machines that MSRT cleaned for the four most prevalent Fireball families suggests that only around 11 million computers were infected.

“We’ve reached out to Check Point and requested to take a closer look at their data,” O’Dea notes.

Contacted by SecurityWeek, Check Point said its estimation for the number of global infections was based on a combination of data from Alexa and from its own ThreatCloud network of sensors.

"Our threat intelligence team has been fully cooperating with Microsoft researchers on their analysis," the company told SecurityWeek in an emailed statement. "We see no logical reason for a user to enter the fake search engine pages if not infected, and relate the gap in the calculated number of infected machines to our analysis being merely an estimation, and to Microsoft’s data relying solely on endpoints with a legally licensed copy of Windows.

*Updated with comment from Check Point.

Related: Fireball Malware Infects 250 Million Computers

Related: This Stealthy Malware Remained Unnoticed for Three Years

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