Russian Crooks Spreading Gozi Trojan with PDFs

Russian cyber-criminals are using malicious PDFs to broadcast a Gozi Trojan variant.

A malicious PDF attack launched earlier this week is downloading a variant of the Gozi Trojan—the same malware thats been used to steal personal data with a black market value of over $2 million, including bank, retail and payment services account numbers as well as Social Security numbers.

SecureWorks, which originally discovered the Gozi Trojan in February 2007, said the latest attack is coming from the same Russian criminals who launched the February attack.

The Russian Business Network—a Russian ISP thats notorious for hosting illegal or shadowy businesses including child pornography, phishing and malware distribution sites—has had to take down two servers that were getting overloaded due to the success of the exploit, according to SecureWorks.


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The criminals are sending out spam with rigged PDF attachments. The PDFs transform a victims PDF reader into a malware installer. After a victim clicks on the PDF, it downloads the Gozi variant. Gozi then captures any data entered into SSL-encoded sites, which includes most Internet banking, online retail and corporate intranets. SecureWorks sources are confirming that the attack is widespread at this point.

The exploit is successfully using a URL-handling vulnerability in Windows XP and Windows Server 2003 running Internet Explorer 7. The rigged PDF file is using a "mailto: option" vulnerability in Adobe Acrobat 8.x to install the Trojan, which in turn is downloading a file that Symantec identified on Oct. 23 as "Downloader." That document is delivered as a piece of spam with a file name such as "BILL.pdf" or "INVOICE.pdf." SecureWorks noted that those names may change.

The spam thats delivering the rigged PDF looks like this:

From: Gilbert

Subject: STATEMET indigene

Date: Tue, 23 Oct 2007 08:08:22 +0000

This latest Gozi variant, Gozi.F, is being detected by only 26 percent of 32 of the largest anti-malware vendors at the time of release, according to SecureWorks.

SecureWorks is recommending that users protect themselves by updating anti-virus signatures and by blocking network traffic to RBN, including FTP traffic to and HTTP traffic to Also, users should be warned to keep away from PDF files or other e-mail attachments from untrusted sources.

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