Dissecting the first Gafgyt bot implementing the “VanillaUPX technique”

Experts at the CSE Cybsec Z-Lab have found a Gafgyt variant implementing the VanillaUPX technique recently presented in a cybersecurity conference

A new variant of the Gafgyt botnet is spreading in the last hours and experts of the CSE Cybsec Z-Lab have found it with the support of the Italian cyber security experts @Odisseus and GranetMan.

The new variant analyzed in the report published by the experts was found on a system resolving the IP address owned by the Italian ISP Aruba. This specific version implements some advanced packing techniques that make the static analysis much harder.

We downloaded the sample directly from the compromised server, we found four samples of the Gafgyt variant that were already compiled for the specific architecture, X86-64, X86-32, MIPS, ARM.

The sample shows the same behavior associated with the classic Gafgyt botnet but we immediately noticed a distinctive feature, the implementation of “VanillaUPX” technique shown in the “Unpacking the non-unpackable” presentation

Malware Must Die leader @unixfreaxjp presented the sophisticated technique at the recent Radare conference (r2con2018) in his talk about the “VanillaUPX” technique.

According to the experts the “VanillaUPX” ELF was around since a few months before the talk and our discovery confirms that malware developers started adopting it.

The report includes a detailed analysis of the malware.

You can download the full ZLAB Malware Analysis Report at the following URL:

http://csecybsec.com/download/zlab/20180919_CSE_Gafgyt_v2.pdf

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Pierluigi Paganini

(Security Affairs – Gafgyt, malware)

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