Analysis by: Mio Fidel Villena

ALIASES:

VBS/Autorun.worm (NAI),VBS/Agent.NLO worm (NOD32), VBS.Dunihi (NORTON)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Worm arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It 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: 43,718 bytes
File Type: VBS
Memory Resident: Yes
Initial Samples Received Date: 29 Jan 2018

Arrival Details

This Worm arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It 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 drops the following copies of itself into the affected system:

  • %User Profile%\ntuser.vbe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

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
ntuser = wscript.exe //B "%User Profile%\ntuser.vbe"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
ntuser = wscript.exe //B "%User Profile%\ntuser.vbe"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
ntuser = wscript.exe //B "%User Profile%\ntuser.vbe"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
ntuser = wscript.exe //B "%User Profile%\ntuser.vbe"

Other System Modifications

This Worm adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\Software\ntuser
{Default} = "{true\false} - {date executed}"

Propagation

This Worm drops the following copy(ies) of itself in all removable drives:

  • {Removable Drive Letter}:\ntuser.vbe

It creates shortcut files (.LNK) disguised as folders or files located on the affected drives pointing to the malware copy.

Dropping Routine

This Worm drops the following files:

  • {Removable Drive Letter}:\{Original Folder Name}.lnk

Other Details

This Worm connects to the following possibly malicious URL:

  • http://{BLOCKED}-lc5.servergame.com

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

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.934.04
FIRST VSAPI PATTERN DATE: 29 Jan 2018
VSAPI OPR PATTERN File: 13.935.00
VSAPI OPR PATTERN Date: 30 Jan 2018

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 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

Terminate the malware/grayware/spyware process:

[ Learn More ]
  1. 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.
  2. 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • ntuser = wscript.exe //B "%User Profile%\ntuser.vbe"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • ntuser = wscript.exe //B "%User Profile%\ntuser.vbe"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
    • ntuser = wscript.exe //B "%User Profile%\ntuser.vbe"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
    • ntuser = wscript.exe //B "%User Profile%\ntuser.vbe"

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
    • ntuser

Step 6

Search and delete these files

[ 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.
  • {Removable Drive Letter}:\{Original Folder Name}.lnk

Step 7

  1. Open a command prompt.
    • For Windows 2000, Windows XP, and Windows Server 2003 users, click Start>Run. In the Search box, type CMD then press Enter.
    • For Windows Vista, Windows 7, and Windows Server 2008 users, click Start, type CMD in the Search input field then press Enter.
    • For Windows 8, Windows 8.1, and Windows Server 2012 users, right-click on the lower-left corner of the screen, click Command Prompt.
  2. In the CMD console, type the following:

    ATTRIB [+R | -R] [+A | -A ] [+S | -S] [+H | -H] [+I | -I] [drive:][path][file name] [/S [/D] [/L]]

    Where:
    + Sets an attribute.
    - Clears an attribute
    R Read-only file attribute
    A Archive file attribute
    S System file attribute
    H Hidden file attribute
    I Not content indexed file attribute
    [drive:][path][filename]
    Specifies a file or files for attrib to process
    /S Processes matching files in the current folder and all subfolders.
    /D Processes folders
    /L Work on the attributes of the Symbolic Link versus the target of the Symbolic Link
    Example:
    To unhide all files and folders (including subfolders) in drive D:
    ATTRIB –H D:\* /S /D
  3. Repeat Step 3 for folders and files in other drives or folders.

Step 8

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

Step 9

Scan your computer with your Trend Micro product to delete files detected as VBS_DUNIHI.ELDSAVE. 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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