DarkGate Malware Abuses AutoIT Scripting For Payload Obfustication

DarkGate is a type of malware that employs Auto-It compiled loaders that cause a considerable threat because of its advanced evasion strategies and persistence within compromised systems.

By using obfuscated AutoIt scripting and multi-stage payloads, the malware makes it more difficult to identify using conventional signature-based techniques.

Meticulous detection and analysis are necessary due to their capacity to obtain command and control communications and exfiltrate sensitive data.

The scripting language AutoIt was created specifically for automating Windows GUI and general scripting tasks. It has been used for malicious purposes throughout history, including AutoIt-compiled malware dating back to 2008.

“Malware creators have exploited the versatility of AutoIT in a variety of ways, such as using obfuscated scripts for payload decryption, utilizing legitimate tools like BaSupportVNC, and even creating worms capable of spreading through removable media and Windows shares”, said Splunk researchers.

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Insights of DarkGate Malware and Its Use of AutoIt

Researchers discovered several campaigns using a loader intended for launching DarkGate on hacked systems. An instance of this would be the discovery of malicious PDF files that serve as carriers and cause a malicious CAB file to be downloaded. 

This CAB file, in turn, downloads a.MSI file containing and loading the DarkGate malware. This file appears to load a series of files, including two.BIN files, a DLL module, and the legitimate wndbg.exe, all of which are necessary for DarkGate to execute.

In a different variation, it adds another .CAB installer to the targeted host’s installation process, expanding its infection strategy. This enhanced strategy highlights threat actors’ ongoing attempts to avoid detection by highlighting the intricacy and sophistication of the infection mechanism they have chosen.

Four.png files are utilized solely as dummies or decoys to hide or mislead the observer from the important parts of the DarkGate operation.

“Within the .CAB file, a collection of files has been identified. Among these files, the pivotal components driving the initiation of DarkGate malware include windbg.exe, dbgeng.dll, data.bin, and data2.bin”, researchers said.

The subsequent stage of this malicious installation of the .CAB file entails the use of windbg.exe to execute a specifically designed dbgeng.dll via DLL side-loading techniques.

Data2.bin contains two encoded files, separated by the ‘splitres’ string. The first file to be decoded from the base64 process is a legitimate Autoit3.exe, which is used to run the second file, which is a script.au3 AutoIt script that has been constructed. 

The final loader encompasses both a shellcode and a .exe file designed to decrypt the DarkGate malware.

Hence, maintaining a strong defense against DarkGate’s shifting techniques requires constant monitoring in addition to updated defense systems.

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