The group behind Emotet malware is getting smarter and smarter in the way
Today I’d like to share a quick analysis resulted by a very interesting email which claimed to deliver a SOC “weekly report” on the victim email. First of all the
SOC report 10 12 2019.doc
firstname.lastname@example.org. I believe that
ambientehomedecor.com is not a malicious
|Threat||Word document Dropper (Emotet)|
|Brief Description||First stage of Emotet campaign targeting organization with Security Operation Centers|
Following the original eMail headers from
email@example.com to victim’s email box it is possible to figure-out the attacker used a SMPT client who left trace about the original sender IP address which happens to be:
188.8.131.52. According to IPLocation that address is related to a very nice town in northern France: Thury-Harcourt, France.
The attached document is a well obfuscated Microsoft Word document which asks to enable macros in order to view its content. The
autoopen function begins a complex obfuscated chain which tries to deter analyst by introducing junk code, junk variable assignments and fake apparent real comments. The following image proves the adopted obfuscation technique. The function
c878cxx90590 is the “Real Code” by meaning is not part of junk code but actually is the function who really performs malicious actions. As you might see being in the middle of hundreds similar lines of code it gets hard to spot.
The obfuscated macro creates on-memory objects and runs them without passing through temporary files. The following image shows the auto-run created object before the Drop’n Execute. The analysed variable in the following image is the
c0639047895c6 which, in that specific run, holds the Win32_ProcessStartup created Object for fulfill persistence on the victim machine.
Once the dropper assured the persistence and to run during the start-up, it carves from itself the following powershell script. The script runs an encoded string hiding the dropping ULRs. The base64 decoded string shows a romantic
foreach statement looping through a list of compromised websites hosting the real payload :
de6a8b8612b5236a18eea1a6a8f53e117d046cf2ad95e079a6715af68f8d2216 (VT 6/69). It finally saves the dropped file in a userprofile location as placed in the variable
xc0x57b38b2x7, before running it. The following image shows the powershell script before and after the encoding by giving a quick description on it.
According to VT, the final run looks like Emotet, a banking trojan who steals credentials, cookies and eCoin wallets. Emotet is also able to access to saved credentials of the major browser like Chromium, Firefox, Opera, Vivaldi to exfiltrate cookies, and to send back to command and control found victim information. But let’s try to quickly check it.
|Threat||Emotet. Data Exfiltration|
|Brief Description||Dropped and Executed by previous stage|
The dropped file (VT 12/69), grabbed from the dropping URLs inside the previous powershell script, is an executable packed by internal functions which uses several techniques to avoid static and dynamic analysis. For example it deletes the original file once executed, it resolves an unusual very high number of APIs and it dynamically resolves functions avoiding static analysis.
During the running phase the analyzed sample records many information on the hosting machine, it asks for local public IP address by querying an external resource: http[://185[.42[.221[.78:443/whoami.php and finally it pushes out those information to external Command and Control (please refer to IoC section for the complete C2 list).
The sample starts a local service called
khmerdefine and assures its persistence by adding that file in
c:\Windows\SysWOW64 and setting up a system service in autorun. AV and plenty static traffic signatures confirm we are facing a new encrypted version of Emotet trojan.
Emotet gang is getting smarter and smarter in delivery artifacts. That time they addressed companies having an external Security Operation Center (SOC) pretending to simulate an external SOC operator who sends periodic reports to the company. The delivery content was a Microsoft word document within heavily obfuscated Macros who eventually drops and executes Emotet Malware. The following image represent the compiled MITRE ATT&CK matrix in order to qualify stages and to describe the overall behavior.
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
The original post is available on Marco Ramilli’s blog:
(SecurityAffairs – Emotet, zero-day)