A new variant of the Gozi banking trojan has infected thousands of machines in the United States and is targeting the master boot record (MBR) of Internet Explorer users.
Researchers at security firm Trusteer revealed that a rootkit, a feature not often found in financial malware, was packaged with the latest version of Gozi.
In a blog post last Thursday, Etay Maor, a Trusteer researcher, explained that the rootkit is particularly difficult to extract.
“Due to their strategic placement in the operating system's kernel, rootkits are difficult to identify and remove,” Maor wrote.
Gozi, packaged with the rootkit, sits silently in the MBR, waiting for Internet Explorer (IE) to launch, he said. Once the browser is running, the trojan injects itself into victims' browsers so it can steal financial information that users enter into sites.
In a Monday interview, Yishay Yovel, vice president of marketing for Trusteer, told SCMagazine.com that the firm detected as many as a couple thousand infections of this variant in the United States.
Yovel said that, despite key leaders in the cyber gang responsible for the malware being caught by federal authorities, the campaign has continued to persist.
In 2010, Nikita Kuzmin, the alleged creator of Gozi, was arrested in the United States, followed by Deniss Calovskis, who allegedly wrote parts of the trojan's code. Calovskis' was arrested in November in Latvia.
Since Gozi first appeared in 2005, federal prosecutors estimate it has infected at least 100,000 computers worldwide, including 25,000 in the United States, causing tens of millions of dollars in losses.
“There was an expectation that Gozi would decline with the arrests, but now we are seeing this evolution,” Yovel said.
Attackers means of distributing the malware has remained the same, he said, with perpetrators using drive-by download or phishing emails to lure users into installing weaponized documents containing the trojan.
To remediate after a Gozi infection, Trusteer reseachers recommend that users do a complete hard drive format, reinstall their operating system and implement enterprise security solutions, prior to updating their online banking credentials.