Showing posts with label #Malware. Show all posts
Showing posts with label #Malware. Show all posts

Thursday, 22 June 2017

Coin Miner Attacks using Image File


I am here to tell about the "story of an image"...

Well, let's gooooooooo!!

Watching the picture below, what you can tel about it? Is it a simple image?


...and in the following picture?

YES!! They are the same picture, the first one is what you can see when you open it. The second one, is what you can see if you open it using for example a simple text editor.

Today I want to tell you about a malware that I discovered during my activity as researcher, malware hunter and malware Analyst.
It uses an image (JPG file) with embed a shellcode in order to infect the Linux System.



Shellcode Analysis:

Image reported above show part of image coded file and embedded shellcode in clear text.

Second line, command "crontab", is a time-based job scheduler in Unix-like computer operating systems.

"Crontab" option "-r" is present only in some Linux distro like Debian, Centos and Redhat. I can image that this malware is focused to Linux distro quoted above.


Third line of shellcode get seconds and transform them in days from 1970, then store them in a variable named"days". 
Sum the value 983 to "days" variable and assign this value to variable named"days2".
Then "days" variable will have the first 10 elements of MD5's digest of  "days2" .

Into shellcode's snippet reported below it is listing processes and concatenate other commands like xargs and awk.
The last one searches files that have text that match the pattern, when a line or text matches, awk performs a specific action on that line/text. In this case concatenating "print $2", it return the second item (proces' ID) and then kill it.

Using command "pkill -f", shellcode kills processes which matches the pattern for any part of the command line

This shellcode's snippet is used to kill any others miner that had infected the machine, in order to be the only one to use it.

"DoMiner" function using Curl command download into "tmp" folder a file image JPG named "car-498167.jpg" from website  "imagehousing[dot]com" and rename this image with "days" variable's value.

Then skips the first 2931 byte and save it again.
After this task file's permission is changed with execution privileges and in the end it use "nohup" command line-utility which allows to run command/process or shell script that can continue running in the background after you logout from a shell.
Sleep and then remove everyone file with name "days" and "daybefore".


NOTE: No part of source code file named "daybefore.jpg" has been created. Only a variable was created using this name.
Why put this shellcode line? Are there typographical error?

Carry on downloading image file "car-498167.jpg" using browser. It looks like the first one.

A quick analysis shows that it doesn't contains evil shellcode or evil artifacts, but I discovered a very interesting information.


As you can read, it is packed with UPX packer, version 3.91. 

I create a bash script in order execute it in debug mode, download image and skip 2931 byte as wrote into source code.

Below you can see my bash script and its result in terms of files.

Note: "12days" and "13days" are names that personally I decided to appoint to this images.

Above you can see both file, the first one (the image file) and the second one (executable file) that is the first one without 2931 bytes. Below you can take a look to the files size.

I used UPX packer to unpack ELF file. Below is reported a screenshot that contains details (format, compression ration, actual and future file size) about ELF executable file.

Now it's time to unpack ELF executable file

Below are reported details about ELF's file.




Shellcode In-depth Analysis:

Working on it and downloading "car-498167.jpg" image I noted that server returns a different image based on "User Agent".
The attacker can return the right file only if the system is x64 and is one of Linux distro reported above.
If it seems incredible take a look to the screenshot reported below. Request was made with Slackware distro.




Analyzing shellcode my attention was attract from string like the follow:
"4Ab9s1RRpueZN2XxTM3vDWEHcmsMoEMW3YYsbGUwQSrNDfgMKVV8GAofToNfyiBwocDYzwY5pjpsMB7MY8v4tkDU71oWpDC".

It is not a string base64 encrypted, what of it?

I retrieved a pastebin file where was present part of this shellcode, where I found the same strings.

As you can see, in this shellcode's snippet, if doesn't exist a file named "AnXqV" "Minerd CryptoCurrency" it is going to download and save into "tmp" folder with file named "AnXqV".
Then execution permission is assigned to this file.
At the end a command named "cryptonight" is running.

NOTE: CryptoNight is a proof-of-work algorithm. It is designed to miner bitcoin and to be suitable for ordinary PC CPUs.

According with handbooks every miner use a different command's format. In case reported above 
command "-a cryptonight -o stratum+tcp://URL:PORT -u WALLET_ADDRESS -p x" is used to run miner. So, string "4Ab9s1RRpueZN2XxTM3vDWEHcmsMoEMW3YYsbGUwQSrNDfgMKVV8GAofToNfyiBwocDYzwY5pjpsMB7MY8v4tkDU71oWpDC" is a Monero's wallet address.



ELF file In-depth Analysis:

Analyzing ELF file I was able to retrieve more information about malware's type, its author and the URLs reached out.

Who create this software have nickname "fireice-uk", below there is a screenshot of his github's account.


Also was possible to retrieve URL that are contacted by this miner


Checking domain owner, like in a fairy tail, website is liked to the Miner's developer (Fireice-UK)


Malware's developer embedded the miner developed by "fireice-uk". If the two person are different, why malware's developer have to use and include a miner developer my another person?

Below you can find evidence about matching between information extracted from ELF's file and source code created by "fireice-uk".

In my opinion who developed malware and miner could be the same person.

Friday, 10 March 2017

New Way to run VBScript Payload


Some day ago I received an email in an unmarked Gmail mail box. It was a clear Phishing email, but what catched my eyes has been a Password reported into the email's body and the attachment. It was a Microsoft Word file with ".docx" extension.

The first question that I asked to myself was: "Why this file wasn't dropped from Google security check?".

I decided to analyze the attachment and investigate about the sender.

First of all, I opened the attachment and putted into the password reported into the email's body. Opened, it had only three icons that looks like word's icons.



My first words were "What a fuck of Word file is this?!?!".
It doesn't makes sense! No text, no request to enable macro on startup.

The total words catch my eye. As you can see into the red circle, they were 369 words, but the document didn't had text, only 3 image's icons.

Double click on the image and I discovered the secret. The macro, VBScript, is embedded within it!

"What?! A macro into an image?!...You are a fucking genius!!" I Thought.

 But in which way is possible to embedded a VBScript into an image?!

The answer of my question was behind the right-click. Who created this document used Packager Shell Object to embed the VBScript content.

Taking a close look to Packager Shell Object properties was easy to understand that it was a VBScript file and where it was it was stored.

It was stored in "\Local\Temp" folder every time the Word file is executed. When the file is going to shut down it is going to be deleted from this folder.



The VBScript was obfuscated, but not in a hard way.

In the snippet code reported below, is reported two different files that are going to be created based on seconds:

  • the first one had extension ".viv"
  • the second one had extension ".qde"
Please note, seconds were used as file's name.



"JAy0D" function reads from file ".qde" and write into the file ".viv".

The snippet code reported below shows the resource that the dropper has to download, file with extension ".pkg".



Using whois protocol, I retrieved domain's information. Is useful to note that this domain is protect by privacy policy agreement.



File format ".pkg" is an installation file used by Apple in its Operating System.

Was impossible to download "tmp.pkg" file. The server gave error 404 Not Found.


Another resource that has to be downloaded is a file ."jpt".
JPT format file (JPEG-PNG-Type) takes advantage of the compression ratio from JPEG and PNG at the same time.
The main image is stored in JPEG while the alpha channel is stored in a PNG file as a gray scale.
While the PNG file can be 32 bit, 24 bit, 8 bit or even palette based, it is recommended to use
only 8 bit or palette based images in order to save space and actually take advantage of the JPT
format.
The next step was to analyze this file.


There I discovered the home page where this library come from.

It was hosted in a github page that it is not longer available.


From the page, I was able to recovery the developer's name "Jake J. Davis" and thanks to Google Cache, part of his GitHub account.

Jakey J. Davis closed a lot of his accounts in the last months, like github, libraries.io, etc.

Another analysis I did was the email's header. Here we can read sender's PC name connected to the server.




 Hey! Bruce, remember: "The first Internet's rule is: Stay Stealth"! 👀


CONCLUSION and HESITATIONs:

Something doesn't seems clear.
  1. File PKG is not reachable.
  2. JTP file doesn't seems to be JTP's format.
  3. This VBScript works only on Windows OS and it acts as a dropper to download other resources. It also use windows like commands ("cmd.exe") to perform some checks ("ping 8.8.8.8");
  4. If everything seems wrote for Windows OS, why it has to download file that works on Mac OS?







In conclusion: Given all these inconsistencies, many questions are still outstanding and this leave us two options, everything is part of a bigger project or the one who created these files is a newbie?


Thanks to my colleague for the support provided! ☺