Chthonic: The Dangerous ZeuS Trojan Attacking You Via Your Bank

A significant new malware threat is targeting online banking systems and their customers, it has been revealed.

The Trojan was discovered by security analysts at Kaspersky Lab and has been identified as an evolution of the infamous ZeuS Trojan, Trojan-Banker.Win32.Chthonic or Chthonic for short, is known to have hit more than 150 different banks and 20 payment systems in 15 countries. It appears to be mainly targeting financial institutions in the UK, Spain, the US, Russia, Japan and Italy.

Exploiting your webcam and keyboard

Chthonic exploits computer functions, including the web camera and keyboard, to steal online banking credentials such as saved passwords. Attackers can also connect to the computer remotely and command it to carry out transactions.

Chthonic’s main weapon, however, is web injectors. These enable the Trojan to insert its own code and images into the bank pages loaded by the computer’s browser, allowing the attackers to obtain the victim’s phone number, one-time passwords and PINs, as well as any login and password details entered by the user.

Victims are infected through web links or by email attachments carrying a document .DOC extension that then establishes a backdoor for malicious code. The attachment contains a specially crafted RTF document, designed to exploit the CVE-2014-1761 vulnerability in Microsoft Office products.

Once downloaded, malicious code that contains an encrypted configuration file is injected into the msiexec.exe process and a number of malicious modules are installed on the machine.
So far Kaspersky Lab has discovered modules that can collect system information, steal saved passwords, log keystrokes, enable remote access, and record video and sound through the web camera and microphone, if present.

In the case of one of the Japanese banks targeted, the malware was able to hide the bank’s warnings and instead inject a script that allows the attackers to carry out various transactions using the victim’s account.

Affected customers of Russian banks are greeted by completely fraudulent banking pages as soon as they log on. This is achieved by the Trojan creating an iframe with a phishing copy of the website that has the same size as the original window.

Chthonic shares some similarities with other Trojans. It uses the same encryptor and downloader as Andromeda bots, the same encryption scheme as Zeus AES and Zeus V2 Trojans, and a virtual machine similar to that used in ZeusVM and KINS malware.

Fortunately, many code fragments used by Chthonic to perform web injections can no longer be used, because banks have changed the structure of their pages and in some cases, the domains as well.

Yury Namestnikov, senior malware analyst at Kaspersky Lab and one of the researchers who worked on the investigation of the threat, said: “The discovery of Chthonic confirms that the ZeuS Trojan is still actively evolving. Malware writers are making full use of the latest techniques, helped considerably by the leak of the ZeuS source code. Chthonic is the next phase in the evolution of ZeuS. It uses Zeus AES encryption, a virtual machine similar to that used by ZeusVM and KINS, and the Andromeda downloader – to target ever more financial institutions and innocent customers in ever more sophisticated ways. We believe that we will undoubtedly see new variants of ZeuS in the future, and will continue to track and analyse every threat to stay one step ahead of the cybercriminals.”

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Duncan Macrae

Duncan MacRae is former editor and now a contributor to TechWeekEurope. He previously edited Computer Business Review's print/digital magazines and CBR Online, as well as Arabian Computer News in the UAE.

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