Analysis by: Denisse Camille Layco
ALIASES:

VBS/QHost.Q!tr (FORTINET)

 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

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: 4,221 bytes
File Type: VBS
Memory Resident: No
Initial Samples Received Date: 20 Nov 2020
Payload: Modifies system registry

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 and executes the following files:

  • %User Temp%\{random characters}.bat -> deleted later

(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).)

It adds the following processes:

  • cmd /C reg add HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced /v HideFileExt /t REG_DWORD /d 1 /f
  • "explorer.exe" {Malware path}\

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
HideFileExt = 1

(Note: The default value data of the said registry entry is user-defined.)

HKEY_CLASSES_ROOT\VBSFile\DefaultIcon
(Default) = %SystemRoot%\system32\SHELL32.dll,3

(Note: The default value data of the said registry entry is %SystemRoot%\system32\WScript.exe,2.)

Other Details

This Trojan adds the following lines or registry entries as part of its routine:

  • HKEY_LOCAL_MACHINE\SOFTWARE\Classes\ VBSFile\DefaultIcon

It adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
VBSFile\DefaultIcon
(Default) = %SystemRoot%\system32\SHELL32.dll,3

It does the following:

  • Drops copies of itself to all subdirectories of the drive where the malware was executed:
    • {Subdirectory name }.vbs
  • Modifies itself to append a new line in the script

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 16.372.03
FIRST VSAPI PATTERN DATE: 25 Nov 2020
VSAPI OPR PATTERN File: 16.373.00
VSAPI OPR PATTERN Date: 26 Nov 2020

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

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 3

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.  
  • {Subdirectory name                                                                      }.vbs

Step 4

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_LOCAL_MACHINE\SOFTWARE\Classes\ VBSFile\DefaultIcon
    • (Default) = %SystemRoot%\system32\SHELL32.dll,3

Step 5

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\Classes\ VBSFile
    • DefaultIcon
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes
    • {space}VBSFile

Step 6

Restore this modified 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\Explorer\Advanced
    • From: HideFileExt = 1
      To: HideFileExt = 0
  • In HKEY_CLASSES_ROOT\VBSFile\DefaultIcon
    • From: (Default) = %SystemRoot%\system32\SHELL32.dll,3
      To: (Default) = %SystemRoot%\system32\WScript.exe,2

Step 7

Scan your computer with your Trend Micro product to delete files detected as Trojan.VBS.QHOST.B. 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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