Analysis by: Francesca Villasanta
ALIASES:

VHO:Backdoor.MSIL.Convagent.gen (KASPERSKY)

 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, Dropped by other malware

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. It may be dropped by other malware.

  TECHNICAL DETAILS

File Size: 11,264 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 01 Mar 2024
Payload: Excludes files in Windows Defender

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.

It may be dropped by the following malware:

Installation

This Trojan adds the following processes:

  • cmd.exe /c PowerShell.exe -windowstyle hidden Add-Mppreference -ExclusionPath %Application Data%\Microsoft\Windows\explorer.exe
  • cmd.exe /c PowerShell.exe -windowstyle hidden Add-Mppreference -ExclusionPath %Application Data%\Microsoft\Windows\Cortana.exe
  • cmd.exe /c PowerShell.exe -windowstyle hidden Add-Mppreference -ExclusionPath %Application Data%\Microsoft\Windows\OneDrive.exe
  • cmd.exe /c PowerShell.exe -windowstyle hidden Add-Mppreference -ExclusionPath %Application Data%\Microsoft\Windows\Templates\svchost.exe
  • cmd.exe /c PowerShell.exe -windowstyle hidden Add-Mppreference -ExclusionPath %Application Data%\Microsoft\Windows\SystemSettings.exe
  • cmd.exe /c PowerShell.exe -windowstyle hidden Add-Mppreference -ExclusionPath %Application Data%\Microsoft\Windows\Taskmgr.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).)

Other Details

This Trojan does the following:

  • It is used to add the following files to the Microsoft Windows Defender's exclusion paths:
    • %Application Data%\Microsoft\Windows\explorer.exe → detected as Backdoor.MSIL.REVENGERAT.BB
    • %Application Data%\Microsoft\Windows\Cortana.exe
    • %Application Data%\Microsoft\Windows\OneDrive.exe
    • %Application Data%\Microsoft\Windows\Templates\svchost.exe → file dropped and executed by Trojan.MSIL.REVENGERAT.BA
    • %Application Data%\Microsoft\Windows\SystemSettings.exe
    • %Application Data%\Microsoft\Windows\Taskmgr.exe

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 19.190.04
FIRST VSAPI PATTERN DATE: 01 Mar 2024
VSAPI OPR PATTERN File: 19.191.00
VSAPI OPR PATTERN Date: 02 Mar 2024

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.XXPE50FFF078 

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

Remove the malware/grayware file dropped/downloaded by Trojan.MSIL.REVENGERAT.BC. (Note: Please skip this step if the threat(s) listed below have already been removed.)

    • Trojan.MSIL.REVENGERAT.BA
    • Backdoor.MSIL.REVENGERAT.BB

Step 5

Scan your computer with your Trend Micro product to delete files detected as Trojan.MSIL.REVENGERAT.BC. 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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