Defeating Guloader Anti-Analysis Technique

Unit 42 researchers recently discovered a Guloader variant that contains a shellcode payload protected by anti-analysis techniques, which are meant to slow human analysts and sandboxes processing this sample. To help speed analysis for this sample and others like it, we are providing a complete Python script to deobfuscate the Guloader sample that is available on GitHub.

In early September 2022, we discovered a Guloader variant with low VirusTotal detection. Guloader (also known as CloudEye) is a malware downloader first discovered in December 2019.

Unit 42 researchers analyzed the control flow obfuscation technique used by this Guloader sample to create the IDA Processor module extension script so researchers can deobfuscate the sample automatically. The script can be applied to other malware families like Dridex, which utilize similar anti-analysis techniques.

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Source: Palo Alto Unit 42