Security Experts:

New Variant of Carberp Trojan Discovered by Researchers

In mid-December, malware developers launched a new version of the notorious Carberp Trojan, a threat designed to steal sensitive information from infected devices.

The first spam campaign for distributing the new version of the malware, detected as Trojan.Carberp.C, was spotted by Symantec researchers on December 15, just one day after the Trojan was apparently compiled.

Carberp.C, like its predecessors, is primarily designed to harvest information, but it can also carry out other tasks with the aid of plugins that are injected into a newly created process (svchost.exe). One of the plugins analyzed by researchers hooks APIs in an effort to steal usernames, passwords and other sensitive data from Web browsers.

The malware is capable of infecting both 32-bit and 64-bit systems and its authors have developed plugins for various CPU architectures, researchers said.

The spam emails discovered by Symantec are designed to look like invoice payment reminders. The Trojan dropper, which is packed with Visual Basic, is attached to these messages as a .ZIP archive file.

Once it’s executed, the dropper injects code into a Windows process, and decrypts and decompresses embedded components. One of these components is MyFault, a legitimate Windows driver used to trigger system crashes for troubleshooting purposes. Experts believe the malware developers are using it to crash the infected device in case the threat is being analyzed.

Another component is the downloader, which silently downloads the payload. The Carberp driver is the component utilized to kill processes and inject malicious payloads into memory in order to keep the infection hidden.

Australia appears to be the main target, but some infections have also been spotted in the United States and elsewhere. It appears cybercriminals are increasingly focusing on Australia. Recent reports show that file-encrypting ransomware has been highly successful in this region over the past period.

The full source code of Carberp was made available on underground forums in June 2013, shortly after Russian authorities announced arresting an individual believed to be the mastermind behind the financial malware. Trojan.Carberp.B was discovered in November 2014, but in the meantime, malware authors also used the source code to create Zberp, a hybrid combining elements from Zeus and Carberp.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.