Info Stealing - The cyber security expert Marco Ramilli spotted a new operation in the wild

The Italia cyber security expert Marco Ramilli, founder of Yoroi, published an interesting analysis of a quite new InfoStealer Malware delivered by eMail to many International Companies.

Attack attribution is always a very hard work. False Flags, Code Reuse and Spaghetti Code  makes impossible to assert “This attack belongs to X”. Indeed nowadays makes more sense talking about Attribution Probability rather then Attribution by itself. “This attack belongs to X with 65% of attribution probability” it would be a correct sentence.

The obtained sample is a Microsoft Word document within macro in it. The macros were heavily obfuscated by using four rounds of substitutions and UTF-8 encoding charsets (which, by the way, is super annoying). The following image shows the obfuscated macro code with UTF-8 charsets.

Stage 1: Obfuscation

By using oletools and “tons” of cups of coffee (to be awake until late night to make recursive steps) I finally was able to extract the invoked command, showed in the following image.

Stage 1: Invoked Command

A fashionable powershell command drops and executes: hxxp://ssrdevelopments.co.za/a2/off.exe. Powershell seems to be a “must have” in contemporary Malware. Analyzing the “dropping” url and tracking down the time it is in “Index Of” mode (2017-0-13), I suspect it is not a compromised website rather a crafted web server or a compromised host of a dead company.

Dropping Web Site

By surfing the Malware propagator website I founded out many malicious executables (sees IoC section) each one showing up specific behaviors such as: password stealers, RAT, and Banking Trojans. Even if the samples were developed for different targets, all of them shared the following basic behaviors:

• Check for victims IP address before getting into Malicious activities (maybe related to targeted activities)
• Install itself into auto execution path
• Tries to fingerprint the target system (such as CPU, HD, Memory, Username, System, etc..)
• Sniff for Keystrokes

I’d like to write a simple analysis for each found sample, but today time is not my friend, so let’s focalize to one of the malicious samples. Let’s get done the received sample by digging into the “second stage” dropped by the pPowerShell “first stage” from ssrdevelopments.co.za/a2/off.exe. After few seconds on second stage (off.exe) it became clear that it was a .NET software. By reversing the interpreted .NET language some clear text comments appeared interesting. Japanese language such as comments and variable names came out from static analysis. Let’s have a look to them.

Stage 2: Apparently Japanese characters

While the sample pretends to be compiled from “Coca-Cola Enterprise” (maybe a target operation against Coca-Cola ? Or a targeted operation agains Coca-Cola Suppliers ? So why it ended up to my inbox ? Anyway … ) google translator suggests me that Japanese characters are in text: such as the “Entry Point”, “Class names” and “Function Names”.

Stage 2: Japanese Names and Self Encoding Structures

It was not hard to figure out that Stage 2 was auto-extracting bytes from itself (local variables) and saving them back to hard drive after having set up auto execution registry key on windows local registry.  The following image shows the xoring function used to decrypt converted bytes to the real payload.

Stage 2: Xoring function to extract Stage 3

On my run, the xored payload took the name of GIL.exe; another .NET  executable. We are now facing the third stage. By analyzing the decompiled sample it became clear that:

• The coding style was quite different from the previous stage (Stage 2)
• The implementation style was different from the previous stage as well
• The sample was interested in information about the user, the machine, the web services on the PC and to many more windows specific parameters.

Stage 3:  New Language in Strings and Class names

Stage 3: New Code Style

By closely investigating Stage 3, the analyst would probably notice the heavy presence of “decorators”, a different format in the definition style and last but not least the core composition. Everything looks like belonging to different single developers. The variable language, the comments structure and the general usage of terms, takes the analyst to believe in having found two different developers belonging to different cultures (maybe countries). Finally the malware looks for users, computes, and web services informations and drops everything up to C2 by posting parameters to : ssrdevelopments.co.za/cgi-bin/

The original post published by Marco Ramilli on his blog at the following URL:

https://marcoramilli.blogspot.it/2017/12/info-stealing-new-operation-in-wild.html

About the author: Marco Ramilli, Founder of Yoroi

I am a computer security scientist with an intensive hacking background. I do have a MD in computer engineering and a PhD on computer security from University of Bologna. During my PhD program I worked for US Government (@ National Institute of Standards and Technology, Security Division) where I did intensive researches in Malware evasion techniques and penetration testing of electronic voting systems.

I do have experience on security testing since I have been performing penetration testing on several US electronic voting systems. I’ve also been encharged of testing uVote voting system from the Italian Minister of homeland security. I met Palantir Technologies where I was introduced to the Intelligence Ecosystem. I decided to amplify my cyber security experiences by diving into SCADA security issues with some of the most biggest industrial aglomerates in Italy. I finally decided to found Yoroi: an innovative Managed Cyber Security Service Provider developing some of the most amazing cyber security defence center I’ve ever experienced ! Now I technically lead Yoroi defending our customers strongly believing in: Defence Belongs To Humans

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