Trojan.VBS.DUNIHI.YYSWR

 Analysis by: Kiyoshi Obuchi

 ALIASES:

VBS/Kryptik.LO (ESET-NOD32); Trojan:Win32/Tiggre!plock (Microsoft);

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • 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.

  TECHNICAL DETAILS

File Size:

951,930 bytes

File Type:

VBS

Memory Resident:

No

Initial Samples Received Date:

05 Apr 2019

Payload:

Drops files, 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:

  • %User Temp%\output.txt -> version number of javaw.exe

(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, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.)

It drops and executes the following files:

  • %Application Data%\CvnLZeQNrI.vbs -> detected as Worm.VBS.DUNIHI.AGV
  • %Application Data%\ntfsmgr.jar -> detected as JAVA_ADWIND.WIL

(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, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, and 8.)

It adds the following processes:

  • {Directory of Java Runtime Environment}\bin\javaw.exe -jar :"%Application Data%\ntfsmgr.jar"
  • "cmd /c " & """" & {Directory of Java Runtime Environment}\bin\javaw.exe & """" & " -version 2> %User Temp%\output.txt"

(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, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, and 8.. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, and 8.)

Autostart Technique

This Trojan creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
ntfsmgr = "{Directory of Java Runtime Environment}\bin\javaw.exe -jar :"%Application Data%\ntfsmgr.jar""

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run (Only when there is successful download)
ntfsmgr = "%Application Data%\jre7\bin\javaw.exe -jar :"%Application Data%\ntfsmgr.jar""

Other System Modifications

This Trojan adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\
Java Runtime Environment (when download is successful)
CurrentVersion = "1.7"

HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\
Java Runtime Environment\1.7 (when download is successful)
JavaHome = "%Application Data%\jre7"

Other Details

This Trojan does the following:

  • accesses the following URL to download a file if {Directory of Java Runtime Environment}\bin\javaw.exe version is not 1.6, 1.7, 1.8 or if {Directory of Java Runtime Environment}\bin\javaw.exe does not exist:
    • http://www.{BLOCKED}dfingerinc.com/images/jre.zip
  • Saves the file it downloads as:
    • %Application Data%\jre.zip
  • However, the URL is inaccessible as of writing.
  • Unzips contents of %Application Data%\jre.zip to the following directory:
    • %Application Data%\jre7

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

14.942.04

FIRST VSAPI PATTERN DATE:

16 Apr 2019

VSAPI OPR PATTERN File:

14.943.00

VSAPI OPR PATTERN Date:

17 Apr 2019

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 Trojan.VBS.DUNIHI.YYSWR

[ 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\JavaSoft\Java Runtime Environment
    • CurrentVersion = "1.7"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment\1.7
    • JavaHome = %Application Data%\jre7
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • ntfsmgr = "%Application Data%\jre7\bin\javaw.exe -jar :"%Application Data%\ntfsmgr.jar""
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • ntfsmgr = "{Directory of Java Runtime Environment}\bin\javaw.exe -jar :"%Application Data%\ntfsmgr.jar""

Step 5

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.  
  • %Application Data%\jre.zip
  • %User Temp%\output.txt

Step 6

Scan your computer with your Trend Micro product to delete files detected as Trojan.VBS.DUNIHI.YYSWR. 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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