Analysis by: Ricardo III Valdez
ALIASES:

UDS:Trojan-Dropper.NSIS.Agent.a (KASPERSKY)

 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: 348,136 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 04 Feb 2023

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 adds the following folders:

  • %User Temp%\subfolder1
  • %User Temp%\{7 Random Characters}.tmp
  • %AppDataLocal%\Deskriptiv155\Hjertere
  • %AppDataLocal%\Deskriptiv155

(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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp 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 drops the following files:

  • %User Temp%\{7 Random Characters}.tmp
  • %User Temp%\{7 Random Characters}.tmp\System.dll
  • %AppDataLocal%\Deskriptiv155\Hjertere\Rouleredes.coe
  • %AppDataLocal%\Deskriptiv155\Hjertere\checkbox_checked.png
  • %AppDataLocal%\Deskriptiv155\Hjertere\Hynde.Una
  • %AppDataLocal%\Deskriptiv155\Hjertere\multimedia-volume-control-symbolic.svg
  • %User Profile%\Music\Petechiate.ini
  • %User Temp%\subfolder1\Windowss.exe

(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(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp 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).. %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).)

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
Startup key = %User Temp%\subfolder1\Windowss.exe

Other Details

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Sansebeskrivelsers
(Default) = (value not set)

HKEY_LOCAL_MACHINE\SOFTWARE\Sansebeskrivelsers\
Vandsamling197
(Default) = (value not set)

HKEY_LOCAL_MACHINE\SOFTWARE\Sansebeskrivelsers\
Vandsamling197\Hybridnettets
(Default) = (value not set)

HKEY_LOCAL_MACHINE\SOFTWARE\Sansebeskrivelsers\
Vandsamling197\Hybridnettets\Energimaengde52
Orientalises = 23 cd 59

HKEY_CURRENT_USER\Software\carboxylsyren
(Default) = (value not set)

HKEY_CURRENT_USER\Software\carboxylsyren\
Fluer172
(Default) = (value not set)

HKEY_CURRENT_USER\Software\carboxylsyren\
Fluer172\Amortisationerne
Socionetr = 11 45 f3

HKEY_LOCAL_MACHINE\SOFTWARE\weighers
Lunefuldest = Alphyls

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 18.238.03
FIRST VSAPI PATTERN DATE: 05 Feb 2023
VSAPI OPR PATTERN File: 18.239.00
VSAPI OPR PATTERN Date: 06 Feb 2023

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:

    • TROJ.Win32.TRX.XXPE50FSX031

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\RunOnce
    • Startup key = %User Temp%\subfolder1\Windowss.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Sansebeskrivelsers\Vandsamling197\Hybridnettets\Energimaengde52
    • Orientalises = 23 cd 59
  • In HKEY_CURRENT_USER\Software\carboxylsyren\Fluer172\Amortisationerne
    • Socionetr = 11 45 f3
  • In HKEY_LOCAL_MACHINE\SOFTWARE\weighers
    • Lunefuldest = Alphyls

Step 6

Delete this registry key

[ 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_LOCAL_MACHINE\SOFTWARE\Sansebeskrivelsers\Vandsamling197\Hybridnettets
    • Energimaengde52
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Sansebeskrivelsers\Vandsamling197
    • Hybridnettets
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Sansebeskrivelsers
    • Vandsamling197
  • In HKEY_LOCAL_MACHINE\SOFTWARE
    • Sansebeskrivelsers
  • In HKEY_CURRENT_USER\Software\carboxylsyren\Fluer172
    • Amortisationerne
  • In HKEY_CURRENT_USER\Software\carboxylsyren
    • Fluer172
  • In HKEY_CURRENT_USER\Software
    • carboxylsyren
  • In HKEY_LOCAL_MACHINE\SOFTWARE
    • weighers

Step 7

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%\{7 Random Characters}.tmp
  • %User Temp%\{7 Random Characters}.tmp\System.dll
  • %AppDataLocal%\Deskriptiv155\Hjertere\Rouleredes.coe
  • %AppDataLocal%\Deskriptiv155\Hjertere\checkbox_checked.png
  • %AppDataLocal%\Deskriptiv155\Hjertere\Hynde.Una
  • %AppDataLocal%\Deskriptiv155\Hjertere\multimedia-volume-control-symbolic.svg
  • %User Profile%\Music\Petechiate.ini
  • %User Temp%\subfolder1\Windowss.exe

Step 8

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Temp%\subfolder1
  • %User Temp%\{7 Random Characters}.tmp
  • %AppDataLocal%\Deskriptiv155\Hjertere
  • %AppDataLocal%\Deskriptiv155

Step 9

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Trojan.Win32.GULOADER.ZTKB-A. 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.


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