A new computer Trojan based on the infamous ZeuS banking malware is targeting users of over 150 banks and payment systems from around the world, security researchers warn.
The new threat, dubbed Chthonic, is based on ZeusVM, a Trojan program discovered in February that is itself a modification of the much older ZeuS Trojan.
"The Trojan is apparently an evolution of ZeusVM, although it has undergone a number of significant changes," security researchers from antivirus vendor Kaspersky Lab said in a blog post. "Chthonic uses the same encryptor 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."
Like ZeuS, Chthonic's main feature is the ability to surreptitiously modify banking websites when opened by victims on their computers. This technique, commonly known as Web injection, is used to add rogue Web forms on banking websites that ask victims for sensitive information, like credit card details or second-factor authorization codes.
However, Chthonic has a modular architecture that allows cybercriminals to extend the Trojan's functionality. The Kaspersky Lab researchers found Chthonic modules designed to collect system information, steal locally stored passwords, log keystrokes, allow remote connections to the computer through VNC, use the infected computer as a proxy server and record video and sound through the computer's webcam and microphone.
According to Kaspersky Lab, there are several Chthonic-based botnets with different configurations, suggesting the malware is being used by different groups.
"Overall, the botnets we are aware of target online banking systems of over 150 different banks and 20 payment systems in 15 countries," the company's researchers said. "The cybercriminals seem most interested in banks in the UK, Spain, the US, Russia, Japan and Italy."
The new Trojan is primarily distributed in two ways: downloaded by another malware program called Andromeda or through rogue emails that contain specially crafted RTF documents which exploit a Microsoft Word vulnerability patched in March.
Chthonic is the next stage in the evolution of ZeuS, which has become a development framework for malware creators, the Kaspersky researchers said.
Launched in 2007, ZeuS quickly became one of the most popular tools used by cybercriminals, primarily because its was being sold on underground forums. Over the years it was used by many gangs to steal online banking credentials from consumers and businesses that were then used to empty their accounts.
In 2011 the ZeuS source code was leaked online some time after its main developer stopped working on it and gave the code to others. This allowed other malware developers to easily modify ZeuS and create custom threats based on it, including Trojan programs like Citadel, Ice IX, ZeusVM and Gameover Zeus.