Analysis by: Abby Roana Javelosa
ALIASES:

TrojanDownloader:O97M/Emotet.CSK!MTB

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size: 163,048 bytes
File Type: DOC
Memory Resident: Yes
Initial Samples Received Date: 19 Jan 2021

Arrival Details

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This Trojan drops the following files:

  • %User Profile%\Xts_nmf\P4188qk\U95D.dll
  • %AppDataLocal%\{random characters}\{random file name}.{random characters}

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name} on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It adds the following processes:

  • cmd cmd cmd cmd /c msg %username% /v Word experienced an error trying to open the file. & P^Ow^er^she^L^L -w hidden -ENCOD {Base64 encoded string}
  • msg {user name} /v Word experienced an error trying to open the file.
  • POwersheLL -w hidden -ENCOD {Base64 encoded string}
  • %System%\rundll32.exe "%AppDataLocal%\{random characters}\{random file name}.{random characters}",Control_RunDLL

(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Autostart Technique

This Trojan creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random file name}.{random characters} = %System%\rundll32.exe "%AppDataLocal%\{random characters}\{random file name}.{random characters}",Control_RunDLL

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.79.100/{random characters}
  • http://{BLOCKED}v.com/images/7FV4Nd/

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 16.486.04
FIRST VSAPI PATTERN DATE: 19 Jan 2021
VSAPI OPR PATTERN File: 16.487.00
VSAPI OPR PATTERN Date: 20 Jan 2021

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

     
    • Downloader.VBA.TRX.XXVBAF01FF012

Step 2

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 3

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 4

Restart in Safe Mode

[ Learn More ]

Step 5

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random file name}.{random characters}=%System%\rundll32.exe "%AppDataLocal%\{random characters}\{random file name}.{random characters}",Control_RunDLL

Step 6

Search and delete these files

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %AppDataLocal%\{random characters}\{random file name}.{random characters}
  • %User Profile%\Xts_nmf\P4188qk\U95D.dll

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Trojan.W97M.EMOTET.ARRJ. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.

Step 8

Enable the macro virus protection in Microsoft Office Applications

[ Learn More ]


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