SonicWall Capture Labs Threat Research Team recently found a new variant sample and activity in June for the TrickBot malware family. This family has been well known for many years, mainly focused on stealing the victim’s online banking information. This variant has been written by developers with slick development skills wrapping its core functionality with a “Squirrel Shooting Game” code base to throw off initial analysis.
It is often called a banker, however, its modular structure allows it to freely add new functionalities without modifying the core bot. This particular variant uses an RSA encryption schema to protect certain areas of its core code along with custom xor encrypted strings. TrickBot also has the ability to continually update itself by downloading new modules from the C&C server and change its configuration on the fly.
The game wrapped malware only serves as an analysis trick to throw off security researchers and others that want to try and analyse its code base. The game code doesn’t ever execute. The longer the sample is able to run the more IP Addresses are generated and connected too. At first initial analysis we’ve seen the sample connect to over 10 IPs. As you close each connection the sample seems to auto rotate the IP Addresses that are established.
The commands that are executed will disable RealtimeMonitoring, stop the service “WinDefend”, and try to delete the service after it’s terminated. Once finished, it will execute a new process called “teut.exe” which is just the original .exe above just in a new location.