VBS_JENXCUS.YKX

March 21, 2014
 Analysis by: Alvin John Nieto
 ALIASES:

Worm:VBS/Jenxcus (Microsoft), VBS.Dunihi (Symantec), Worm.Win32.VBS.Jenxcus (Ikarus)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This worm arrives via removable drives. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It drops copies of itself into all the removable drives connected to an affected system.

  TECHNICAL DETAILS

File Size:

295,806 bytes

File Type:

VBS

Memory Resident:

Yes

Initial Samples Received Date:

19 Mar 2014

Arrival Details

This worm arrives via removable drives.

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 file(s)/component(s):

  • A:\{random name}.lnk
  • A:\{random name}.exe
  • A:\AutoRun.inf
  • A:\AutoRun.lnk
  • A:\AutoRun.ini
  • A:\movies.exe
  • A:\movies.lnk
  • A:\Copy of dunihi-decrypt.vbs
  • A:\Copy of dunihi-decrypt.lnk
  • A:\x.mpeg
  • A:\x.lnk
  • A:\kihas.exe
  • A:\kihas.lnk

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

  • %User Temp%\{malware name}

(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 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
{malware name} = "wscript //B "%User Temp%\{malware name}""

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
{malware name} = "wscript //B "%User Temp%\{malware name}""

It drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\{malware name}

(Note: %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, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)

Other System Modifications

This worm adds the following registry keys as part of its installation routine:

HKEY_LOCAL_MACHINE\Software\{malware name}

Propagation

This worm drops copies of itself into all the removable drives connected to an affected system.

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}sdly.no-ip.org

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.674.05

FIRST VSAPI PATTERN DATE:

19 Mar 2014

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

Restart in Safe Mode

[ Learn More ]

Step 3

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

 HKEY_LOCAL_MACHINE\Software\{malware name}

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
    • {malware name} = "wscript //B "%User Temp%\{malware name}""
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    • {malware name} = "wscript //B "%User Temp%\{malware name}""

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.
  • %User Temp%\{malware name}
  • %User Startup%\{malware name}
  • A:\{random name}.lnk
  • A:\{random name}.exe
  • A:\AutoRun.inf
  • A:\AutoRun.lnk
  • A:\AutoRun.ini
  • A:\movies.exe
  • A:\movies.lnk
  • A:\Copy of dunihi-decrypt.vbs
  • A:\Copy of dunihi-decrypt.lnk
  • A:\x.mpeg
  • A:\x.lnk
  • A:\kihas.exe
  • A:\kihas.lnk

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as VBS_JENXCUS.YKX. 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 this Knowledge Base page for more information.


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