Analysis by: John Rainier Navato
ALIASES:

UDS:Trojan.MSIL.Taskun.gen (KASPERSKY)

 PLATFORM:

Windows

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

  • Threat Type: Trojan Spy

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

This Trojan Spy 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: 824,832 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 01 Sep 2023
Payload: Connects to URLs/IPs, Deletes files, Drops files

Arrival Details

This Trojan Spy 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 Spy adds the following folders:

  • %System%\Tasks\Updates

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It drops the following files:

  • %Application Data%\{9 Random Characters}.exe
  • %User Temp%\tmp{4 Random Characters}.tmp
  • %User Temp%\{8 Random Characters 1}.{3 Random Characters 1}.ps1
  • %User Temp%\{8 Random Characters 2}.{3 Random Characters 2}.psm1
  • %System%\Tasks\Updates\{9 Random Characters}
  • %User Temp%\{7 Random Characters 1}.tmp
  • %User Temp%\{7 Random Characters 2}.tmp

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %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).. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It adds the following processes:

  • "%System%\WindowsPowerShell\v1.0\powershell.exe" Add-MpPreference –ExclusionPath "%Application Data%\{9 Random Characters}.exe"
  • "%System%\schtasks.exe\" /Create /TN "Updates\"{9 Random Characters}" /XML "%User Temp%\tmp{Random}.tmp"
  • {Malware File Path}\{Malware File Name}.exe

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

Other System Modifications

This Trojan Spy deletes the following files:

  • %User Temp%\tmp{4 Random Characters}.tmp
  • %User Temp%\{8 Random Characters 1}.{3 Random Characters 1}.ps1
  • %User Temp%\{8 Random Characters 2}.{3 Random Characters 2}.psm1
  • %System%\Tasks\Updates\{9 Random Characters}
  • %User Temp%\{7 Random Characters 1}.tmp
  • %User Temp%\{7 Random Characters 2}.tmp

(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).. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Other Details

This Trojan Spy connects to the following possibly malicious URL:

  • https://{BLOCKED}fy.org
  • http://{BLOCKED}indowsupdate.com/msdownload/update/v3/static/trustedr/en/disallowedcertstl.cab?{Random}
  • tcp://{BLOCKED}0.vietnetnam.com:587
  • http://{BLOCKED}.{BLOCKED}.{BLOCKED}.34

It does the following:

  • It creates the following scheduled task:
    • Task Name: Updates\{9 Random Characters}
      Triggers:
      • At log on
      • At task creation/modification
      Task Action: %Application Data%\{9 Random Characters}.exe

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

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 18.682.01
FIRST VSAPI PATTERN DATE: 07 Sep 2023
VSAPI OPR PATTERN File: 18.683.00
VSAPI OPR PATTERN Date: 28 Sep 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:

     
    • Ransom.Win32.TRX.XXPE50FFF072

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

Deleting Scheduled Tasks while in Safe Mode

  1. Still in safe mode, the following {Task Name}-{Task to be run} listed should be used in the steps identified below:
    • Task Name: Updates\{9 Random Characters}
    • Task Action: %Application Data%\{9 Random Characters}.exe
  2. For Windows 7 and Server 2008 (R2) users, click Start>Computer.
    • For Windows 8, 8.1, 10, and Server 2012 users, right-click on the lower left corner of the screen, then click File Explorer.
  3. In the Search Computer/This PC input box, type:
    • %System%\Tasks\{Task Name}
  4. Once located, select the file then press SHIFT+DELETE to delete it.
  5. Open Registry Editor. To do this:
    • For Windows 7 and Server 2008 (R2) users, click the Start button, type regedit in the Search input field, and press Enter.
    • For Windows 8, 8.1, 10, and Server 2012 (R2) users, right-click on the lower left corner of the screen, click Run, type regedit in the text box
  6. In the left panel of the Registry Editor window, double-click the following:
    • HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Schedule>TaskCache>Tree>{Task Name}
  7. Locate the created entry and take note of the registry value's data:
    • ID={Task Data}
  8. After taking note of the data, delete the registry key:
    • HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Schedule>TaskCache>Tree>{Task Name}
  9. In the left panel of the Registry Editor window, double-click the following:
    • HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Schedule>TaskCache>Tasks
  10. Still in the left panel, locate and delete the registry key with the same name as the located Task Data in step #6:
    • ={Task Data}
  11. Close Registry Editor.

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.
  • %Application Data%\{9 Random Characters}.exe
  • %User Temp%\tmp{4 Random Characters}.tmp
  • %User Temp%\{8 Random Characters 1}.{3 Random Characters 1}.ps1
  • %User Temp%\{8 Random Characters 2}.{3 Random Characters 2}.psm1
  • %System%\Tasks\Updates\{9 Random Characters}
  • %User Temp%\{7 Random Characters 1}.tmp
  • %User Temp%\{7 Random Characters 2}.tmp

Step 7

Search and delete this folder

[ 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.
  • %System%\Tasks\Updates

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TrojanSpy.Win32.NEGASTEAL.YXDIAZ. 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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