A dangerous new banking Trojan that combines elements from multiple existing malware tools has affected at least 14 banks in Japan and could be used to attack banks in other regions as well.
Security researchers at IBM Security X Force who discovered the Trojan have dubbed it Shifu and labeled it a particularly sophisticated threat for its range of malicious capabilities.
The Trojan is designed to steal a wide range of banking related information such as usernames and passwords to financial accounts, credentials that users key into HTTP forms, private certificates, and even external authentication tokens used by some banks, researchers say. The data has enabled Shifu’s operators to take over customer bank accounts at multiple Japanese banks.
Shifu also is capable of stealing data from smartcards if it discovers a smartcard reader attached to the compromised endpoint. The malware can search for and steal from cryptocurrency wallets on infected systems and can detect if it has landed on a point-of-sale system, in which case it proceeds to steal payment card data as well.
The Trojan borrows heavily from banking Trojans like Shiz, Gozi, Dridex, and Zeus, IBM says. For instance, the Domain Generation Algorithm that Shifu uses to generate random domain names for botnet communications is the same as the one used in Shiz.
The obfuscation and malware evasion techniques employed by Shifu, including the disabling of anti-virus tools, are borrowed from the infamous Zeus banking Trojan. The command execution method used by Shifu to hide itself in the Windows file system is an exact replica of Gozi, while the malware’s tendency to wipe the local System Restore point to hide its tracks on infected machines is similar to the Conficker worm of 2009.
The techniques used by Shifu to steal passwords, authentication tokens and other credentials and sensitive data from infected system are similar to those employed in the Corcow banking Trojan from 2014 that was targeted at banks in Russia and Ukraine.
“It’s like a Frankenstein of Trojans. It’s an uber patchwork” of malware, says Limor Kessem, senior IBM security evangelist. Whoever assembled Shifu knew enough to take the best features from previous banking Trojans and mash it together along with some powerful new techniques, Kessem says.
One of the more interesting features of the Trojan is how it tries to prevent other malware from infecting systems that it has already compromised, says Kessem.
Once Shifu infects a machine, it launches an antivirus-like feature that actively scans for and prevents other malware from getting downloaded and installed on the same machine.
The Trojan continuously monitors the processes of multiple Internet-connected applications on an infected system and keeps an eye on any incoming files received by the endpoint. Files are blocked if they originate from insecure HTTP connections, or if they are unsigned or are executable.
Files that Shifu identifies as malicious are copied to the local disk, labeled “infected.exx” and uploaded to the mast command and control server. It then sends an “Out of Memory” message to the system trying to execute the malicious file on the infected system, the IBM researchers say.
Many Trojans are designed to block other malware that might be previously installed on the same system from executing or from communication with its command and control server. The differnce with Shifu is that it's the first Trojan that actively blocks new malware from being dropped on a system that it has already infected, Kessem says.
For the moment, the threat appears confined to Japan, but there is little to prevent the malware from being used to target banks in other regions as well, she says. Changing out the trigger list on the malware takes only a few minutes so replacing the list of Japanese banks with a fresh list of banks.
“This is a mash of the old and the new. I think it is going to become more of a threat down the road,” Kessem says.