Worm.VBS.DUNIHI.AAYSYU

 Analysis by: Carlos Villegas Madrid

 ALIASES:

VBS/Agent.NHT worm (NOD32)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet


This Worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It executes commands from a remote malicious user, effectively compromising the affected system.

It gathers certain information on the affected computer.

  TECHNICAL DETAILS

File Size:

196,608 bytes

File Type:

VBS

Memory Resident:

Yes

Initial Samples Received Date:

18 May 2023

Payload:

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

Arrival Details

This Worm 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 Worm adds the following folders:

  • {Infected Removable Drive Letter}:\KaeQrnvNzZ

It drops the following files:

  • %User Temp%\eco\{Malware File Name}.vbs
  • %User Temp%\eco\svchost.exe
  • %User Startup%\{Malware File Name}.vbs
  • {Infected Removable Drive Letter}:\KaeQrnvNzZ\{Malware Name}.vbs → attributes set to System & Hidden

(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).. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows 2003(32-bit), XP and 2000(32-bit), or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit), 10(64-bit).)

It adds the following processes:

  • "%User Temp%\eco\svchost.exe" //B "%User Temp%\eco\{Malware File Name}.vbs"

(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).)

Autostart Technique

This Worm adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{Malware File Name} = %User Temp%\eco\svchost.exe //B "%User Temp%\eco\{Malware File Name}.vbs"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{Malware File Name} = %User Temp%\eco\svchost.exe //B "%User Temp%\eco\{Malware File Name}.vbs"

Other System Modifications

This Worm adds the following registry entries:

HKLM\SOFTWARE\{Malware File Name}
(Default) = false - {Malware Execution Date}

Backdoor Routine

This Worm executes the following commands from a remote malicious user:

  • "execute" - Executes arbitrary command from the C&C server
  • "update" - Updates malware code and restart the malware
  • "uninstall" - Uninstalls the malware
  • "send" - Downloads a file from the C&C server, saves it in a specified directory and run it
  • "site-send" - Downloads a file from the C&C server and run it
  • "recv" - Sends a file from a specified URL to the C&C server
  • "enum-driver " - Retrieves list of drives
  • "enum-faf" - Retrieves information about files and folders in a specified directory
  • "enum-process" - Retrieves information about running processes
  • "cmd-shell" - Executes a command using Command Prompt and retrieves its output
  • "delete" - Deletes a file or folder
  • "exit-process" - Forcefully terminates a process and all its children
  • "sleep" - Running script sleeps for a specified amount of time

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}n.twilightparadox.com:1186/is-ready

Information Theft

This Worm gathers the following information on the affected computer:

  • Computer Name
  • Username
  • OS Information
  • Volume Serial Number
  • Every Antivirus Installed in System
  • USB spreading report

Other Details

This Worm adds the following registry keys:

HKLM\SOFTWARE\{Malware File Name}

It does the following:

  • It sets the attributes of non-LNK files and folders in the infected drive to System & Hidden

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.468.04

FIRST VSAPI PATTERN DATE:

26 May 2023

VSAPI OPR PATTERN File:

18.469.00

VSAPI OPR PATTERN Date:

27 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

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

Identify and terminate files detected as Worm.VBS.DUNIHI.AAYSYU

[ 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 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\{Malware File Name}
    • (Default) = false - {Malware Execution Date}
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {Malware File Name} = %User Temp%\eco\svchost.exe //B "%User Temp%\eco\{Malware File Name}.vbs"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • {Malware File Name} = %User Temp%\eco\svchost.exe //B "%User Temp%\eco\{Malware File Name}.vbs"

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\{Malware File Name}

Step 6

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.
  • %User Temp%\eco\{Malware File Name}.vbs
  • %User Temp%\eco\svchost.exe
  • %User Startup%\{Malware File Name}.vbs
  • {Infected Removable Drive Letter}:\KaeQrnvNzZ\{Malware Name}.vbs

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.
  • {Infected Removable Drive Letter}:\KaeQrnvNzZ

Step 8

Scan your computer with your Trend Micro product to delete files detected as Worm.VBS.DUNIHI.AAYSYU. 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:


Did this description help? Tell us how we did.