Analysis by: Augusto II Remillano

ALIASES:

W97M/Drop.Agent.ylarw (Antivir), DOC/TrojanDropper.Agent.EX trojan (NOD32), Trojan.Mdropper (Norton)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Via email

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 582,041 bytes
File Type: DOC
Memory Resident: No
Initial Samples Received Date: 26 Jun 2018
Payload: Drops files

Arrival Details

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It 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 Temp%\BlocK.txt - a blank text file
  • %User Temp%\decoy.doc - a blank Microsoft Word document

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.)

It drops and executes the following files:

  • %User Temp%\iNteldriVerupd1.sCt - detected as TROJ_STARTER.TJBGBX, contains a VBS scriptlet that runs %User Temp%\TasK.BaT
  • %User Temp%\TasK.BaT - creates %User Temp%\BlocK.txt and executes %User Temp%\2nd.bat
  • %User Temp%\2nd.bat - detected as TROJ_STARTER.TJBGBX. Executes the malware's payload (%User Temp%\ExE.exe), closes Winword.exe, deletes Resiliency registry keys and overwrites a file with %User Temp%\decoy.doc. This batch script will then open the overwritten file.
  • %User Temp%\ExE.exe - The malware's payload. Detected as TSPY_SWOTTER.THFBOAJ.

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.)

Other System Modifications

This Trojan deletes the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Office\11.0\Word\
Resiliency

HKEY_CURRENT_USER\Software\Microsoft\
Office\12.0\Word\
Resiliency

HKEY_CURRENT_USER\Software\Microsoft\
Office\14.0\Word\
Resiliency

HKEY_CURRENT_USER\Software\Microsoft\
Office\15.0\Word\
Resiliency

HKEY_CURRENT_USER\Software\Microsoft\
Office\16.0\Word\
Resiliency

Dropping Routine

This Trojan takes advantage of the following software vulnerabilities to drop malicious files:

Other Details

This Trojan connects to the following possibly malicious URL:

  • hxxp://{BLOCKED}u/newbuild/t.php?thread=0&stats=send

However, as of this writing, the said sites are inaccessible.

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 14.342.07
FIRST VSAPI PATTERN DATE: 26 Jun 2018
VSAPI OPR PATTERN File: 14.343.00
VSAPI OPR PATTERN Date: 27 Jun 2018

Step 1

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

Step 2

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 3

Search and delete this file

[ 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.
  • %User Temp%\decoy.doc
  • %User Temp%\ExE.exe
  • %User Temp%\TasK.BaT
  • %User Temp%\2nd.bat
  • %User Temp%\iNteldriVerupd1.sCt
  • %User Temp%\BlocK.txt

Step 4

Scan your computer with your Trend Micro product to delete files detected as TROJ_STARTER.TJBGBX. 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 the following Trend Micro Support pages for more information:

Step 5

Download and apply these security patches Refrain from using these products until the appropriate patches have been installed. Trend Micro advises users to download critical patches upon release by vendors.


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