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TrojanSpy.MSIL.EXMATTER.C

October 10, 2022
 Analysis by: Carlos Villegas Madrid
 ALIASES:

MSIL/Spy.Exmatter.A trojan (NOD32)

 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.

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

  TECHNICAL DETAILS

File Size:

1,336,320 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

28 Sep 2022

Payload:

Connects to URLs/IPs

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 processes:

  • "%System%\WindowsPowerShell\v1.0\powershell.exe" -C "Stop-Process -Id {Process ID}; Start-Sleep 3; Set-Content -Path '{Malware Folder}\{Malware Filename}' -Value 0" → "melt function" after successful execution it executes a powershell script to overwrite itself leaving a 0 value

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

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • user2user3

Information Theft

This Trojan Spy accepts the following parameters:

  • --background or -b → executes itself with its window hidden
  • --nomutex or -nm → no mutex creation
  • -t → inputs specific number of threads

Other Details

This Trojan Spy does the following:

  • It takes ownership of its executable folder and removes all other account’s access
  • The files it sends must be from 1 year ago up to 6 years ago from its execution date
  • The files it sends must be from 6 months ago up to 10 years from its execution date
  • It does not send system files, temporary files, and directories
  • It does not send files smaller than 8192 bytes
  • It does not send files larger than 67108864 bytes
  • It does not send files from the following directories:
    • \System Volume Information
    • C:\Users\All Users\Microsoft
    • C:\ProgramData
    • C:\Windows
    • C:\$Recycle.Bin
    • C:\Documents and Settings
    • C:\PerfLogs
    • AppData\Roaming\Microsoft
    • C:\Program Files (x86)
    • AppData\Local\Microsoft
    • AppData\Local\Packages
    • C:\Program Files
    • C:\Program Files (x86)
  • It uploads files with the ff. extensions:
    • ppt
    • doc
    • docx
    • docm
    • xls
    • xlsx
    • xlsm
    • ppt
    • pptx
    • pptm
    • xps
    • accdb
    • png
    • jpg
    • jpeg
    • txt
    • bmp
    • rdp
    • sql
    • sqlite
    • db
    • json
    • msg
    • pst
    • zip
    • rtf
    • ipt
    • dwg
  • Creates a directory at the following URLs where it uploads the files:
    • http://{BLOCKED}.{BLOCKED}.41.58/data
    • {BLOCKED}.{BLOCKED}.41.58 → uploads files via SFTP with predefined credentials

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

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

17.862.04

FIRST VSAPI PATTERN DATE:

08 Oct 2022

VSAPI OPR PATTERN File:

17.863.00

VSAPI OPR PATTERN Date:

09 Oct 2022

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.XXPE50FFF060

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

Identify and terminate files detected as TrojanSpy.MSIL.EXMATTER.C

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 5

Scan your computer with your Trend Micro product to delete files detected as TrojanSpy.MSIL.EXMATTER.C. 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:


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