Russia-linked Hackers Use New Trojans in Recent Attacks

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Russia-linked threat group Turla has released new variants of the KopiLuwak Trojan in attacks detected since the beginning of this year, Kaspersky’s security researchers reveal.

Also known as Venomous Bear, Waterbug, and Uroboros, the threat actor was discovered in 2014, but its roots go back at least a decade before. The group is mainly focusing on diplomatic and government-related targets in the Middle East, Central and Far East Asia, Europe, North and South America and former Soviet bloc nations.

This year, Turla has been updating its portfolio of tools, albeit using a familiar coding style. One of the previously tools used by the group is LightNeuron, a sophisticated backdoor designed to hijack Microsoft Exchange mail servers.

In a new report detailing a tool named Topinambour (aka Sunchoke – the Jerusalem artichoke) and its related modules, Kaspersky reveals that Turla has built .NET and PowerShell versions of the KopiLuwak Trojan and has been using these in an active campaign that started in the beginning of this year. 

Infected legitimate software installers are used to spread Topinambour. A tiny .NET shell in the dropper is used to deliver commands to the target machine and spread the next-stage modules via SMB (Server Message Block).

The dropper used in these attacks can deliver the payload to a certain local path, gain persistence for the payload with a scheduled task that starts every 30 minutes, and drop the original application it tries to mimic. 

The small .NET shell dropped in the beginning is used to contact the command and control (C&C) server and fetch the KopiLuwak dropper, which was meant to create a scheduler task, fingerprint the host machine, and drop a JavaScript file that leads to the final stage, a more complex Trojan that can parse and execute custom commands from the C&C.

The .NET Trojan used in addition to the KopiLuwak JavaScript is called RocketMan and supports commands to download/upload a file to/from the victim machine, and stop the Trojan operation. 

The PowerShell Trojan used in the Topinambour campaign is called MiamiBeach. The module is quite similar to the .NET RocketMan Trojan and can handle the same commands, but can also take a screenshot.

“Using the Windows system registry to store encrypted data that is later used by the malware also seems to be aimed at minimizing detection and reducing the digital footprint on any victim’s computer, where only a tiny starter would be left,” the researchers note

The threat actor might have decided to build KopiLuwak’s PowerShell and .NET counterparts to minimize detection of the well-known, publicly discussed JavaScript versions. The use of this Trojan, along with well-known and exclusive artefacts previously associated with the threat actor, have allowed Kaspersky to attribute the campaign to Turla with high confidence.

Related: Russia-Linked Hackers Hijack Infrastructure of Iranian Threat Group

Related: Turla Uses Sophisticated Backdoor to Hijack Exchange Mail Servers

Ionut Arghire is an international correspondent for SecurityWeek.

Previous Columns by Ionut Arghire:
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