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Trojan.Win32.DOWNLOADER.BB

May 17, 2023
 Analysis by: Melvin Jhun Palbusa
 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet


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:

1,071,776 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

15 May 2023

Payload:

Drops files, Modifies system registry, Connects to URLs/IPs

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 drops the following files:

  • {Malware File Path}\config.ini

Other System Modifications

This Trojan adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\
Windows\CurrentVersion\Uninstall\
MaiGuangOffice
(Default) = (value not set)

HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\
Windows\CurrentVersion\Uninstall\
MaiGuangOffice
DisplayIcon = {Malware File Path}

HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\
Windows\CurrentVersion\Uninstall\
MaiGuangOffice
DisplayVersion =

HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\
Windows\CurrentVersion\Uninstall\
MaiGuangOffice
DisplayName = {Foreign Character}

HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\
Windows\CurrentVersion\Uninstall\
MaiGuangOffice
InstallLocation = {Malware File Path}\MaiGuangOffice.exe

HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\
Windows\CurrentVersion\Uninstall\
MaiGuangOffice
Publisher = {Foreign Character}

HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\
Windows\CurrentVersion\Uninstall\
MaiGuangOffice
UninstallString = {Malware File Path}\uninst.exe

Other Details

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\
Windows\CurrentVersion\Uninstall\
MaiGuangOffice

It connects to the following possibly malicious URL:

  • https://{BLOCKED}rtech.com/maiguang?pid=&mid2=6ecec65154d63f22ccc519f7fe9fb70571f934132947&appver=&modver=1.0.0.1025&type=maiguangspeed&action=run&app=

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.448.03

FIRST VSAPI PATTERN DATE:

16 May 2023

VSAPI OPR PATTERN File:

18.449.00

VSAPI OPR PATTERN Date:

17 May 2023

Step 1

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 2

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.  
  • {Malware File Path}\config.ini

Step 3

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.

  • HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\Windows\CurrentVersion\Uninstall\MaiGuangOffice
    • (Default) = (value not set)
  • HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\Windows\CurrentVersion\Uninstall\MaiGuangOffice
    • DisplayIcon = {Malware File Path}
  • HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\Windows\CurrentVersion\Uninstall\MaiGuangOffice
    • DisplayName = {Foreign Character}
  • HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\Windows\CurrentVersion\Uninstall\MaiGuangOffice
    • DisplayVersion = {null}
  • HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\Windows\CurrentVersion\Uninstall\MaiGuangOffice
    • InstallLocation = {Malware File Path}\MaiGuangOffice.exe
  • HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\Windows\CurrentVersion\Uninstall\MaiGuangOffice
    • Publisher = {Foreign Character}
  • HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\Windows\CurrentVersion\Uninstall\MaiGuangOffice
    • UninstallString = {Malware File Path}\uninst.exe

Step 4

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.

  • HKEY_LOCAL_MACHINE\SOFTWARE\MIcrosoft\Windows\CurrentVersion\Uninstall\MaiGuangOffice

Step 5

Scan your computer with your Trend Micro product to delete files detected as Trojan.Win32.DOWNLOADER.BB. 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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