Q&A Does Anyone Know a Detailed Analysis of FusionCore Within a Year?

ZevinZenph

Level 1
Mar 10, 2015
30
Just a quick question: does anyone know a published analysis of the FusionCore (a.k.a. InstallCore) adware?

From what I can recall, this strain of adware was quite infamous back in early 2018 or even prior. It used to be distributed as executable on malicious websites. However, I saw it turning into DLLs embedded in official installers of multiple supposedly legitimate software from some time during 2019, and I cannot find any detailed analysis against its heavily packed files since.

I'm particularly interested in this strain of adware as it's incorporated into many legit installers such as FileZilla and PotPlayer with constantly increasing file size (from ~1MB in mid-2019 to almost 3MB months ago). And I'm quite curious about what they're hiding from our plain sight with this much effort in packaging. The detection rates are always quite high. Sadly, I do not have the skills to analyze native samples (which require advanced knowledge of assembly) and I don't have time to learn the required skills either.

Could anyone also interested in this piece of adware give an analysis, please? The most recent one I can find was from the official FileZilla client v3.53.1.

Spoiler: direct download link of the mentioned installer:
hxxps://download.filezilla-project[.]org/client/FileZilla_3.53.1_win32_sponsored-setup.exe

The embedded FusionCore DLL on VT:

Hashes of the embedded FusionCore DLL:
  • MD5: 0c13d40be85db4ae00f0a6fa14110556
  • SHA-1: 4ffe673e3696a4287ab4a9c816d611a5fff56858
  • SHA-256: 2c16ac58e8943d1f5854f04cd4ebe5fa905e85884c98bc1c14cedb1115de6e71

From the static analysis given by multiple online services, I guess the following properties of those DLLs caught my eyes:
  • All of them are flagged as supposedly written in Delphi (which I guess would be a decoy).
  • All of them have their main payloads encrypted (according to their high entropy) and stored in CODE section (which I guess is the same as .text section).
  • All of them have randomized exported function names mimicking English words.

Much appreciated!
 

ZevinZenph

Level 1
Mar 10, 2015
30
Does this help in any way?

Thank you for the info! What I'm looking for is actually more of a dissection that shows how the packer works and what is in the unpacked payloads like this: Operation TunnelSnake (this is of course an extremely detailed one as its published by dedicated malware researchers). I feel like similar reports may have already been available on the Internet as the detection rates are quite high across most samples, but I just cannot find one.
 
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