Security Experts:

Chthonic Trojan Targets Online Banking Systems in 15 Countries

A new banking Trojan that appears to be an evolved version of the notorious Zeus has been analyzed by researchers at Kaspersky Lab.

According to the security firm, the threat, dubbed Chthonic, borrows some techniques from other pieces of malware, but it also uses some new mechanisms. Detected by Kaspersky as Trojan-Banker.Win32.Chthonic, the Trojan has been used to target a large number of financial organizations in several countries.

Cybercriminals have been distributing Chthonic with the aid of emails carrying malicious documents, and by directly downloading the threat to victim devices using the Andromeda bot. It's worth noting that the Trojan uses the same encryptor as Andromeda.

In the first phase of the attack, a Trojan downloader, which is based on Andromeda source code, is planted on the victim machine. The downloader contains a configuration file that is encrypted using techniques previously seen at KINS and ZeusVM.

The downloader uploads some information to the command and control (C&C) server, after which it receives an extended loader that loads Chthonic's main module. This main module loads additional modules that can be used to carry out specific tasks. Most of these modules are designed to work on 64-bit systems as well.

There are modules for collecting system information, stealing saved passwords, keylogging, Web injections and form grabbing, and remote access. There is also a proxy server module and one designed to capture video via the webcam.

Chthonic uses Web injections to obtain login credentials, PINs, one-time passwords, transaction authentication numbers (TAN), and other sensitive information from victims.

"Our analysis of attacks against customers of Russian banks has uncovered an unusual web injection scenario. When opening an online banking web page in the browser, the entire contents of the page is spoofed, not just parts of it as in an ordinary attack. From the technical viewpoint, the Trojan creates an iframe with a phishing copy of the website that has the same size as the original window," Kaspersky noted in a blog post.

The Trojan is designed to target the websites of more than 150 different banks and 20 payment systems from a total of 15 countries. The highest number of targeted organizations is in the UK (43), followed by Spain (36), the US (35), Russia (22), Japan (18) and Italy (13).

Experts have pointed out that in many cases the Web injections no longer work because the targeted financial organizations have changed their websites and their domains.

"We can see that the ZeuS Trojan is still actively evolving and its new implementations take advantage of cutting-edge techniques developed by malware writers. This is significantly helped by the ZeuS source code having been leaked. As a result, it has become a kind of framework for malware writers, which can be used by anyone and can easily be adapted to cybercriminals' new needs," Kaspersky noted.

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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.