VBS_JENXCUS.YXH

 Analysis by: Janus Agcaoili

 ALIASES:

Worm:VBS/Jenxcus.K (Microsoft), Trojan-Downloader.VBS.Agent.apz (Kaspersky), Worm.VBS.Jenxcus (Ikarus)

 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 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.

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

  TECHNICAL DETAILS

File Size:

1,327,379 bytes

File Type:

VBS

Memory Resident:

Yes

Initial Samples Received Date:

22 Dec 2015

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):

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

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

  • %User Temp%\{malware name}

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

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,exe //B "%User Temp%\{malware name}""

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Run
{malware name} = "wscript.exe //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:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

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://ecu-sec.{BLOCKED}d.jp:1830/is-ready

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

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.260.06

FIRST VSAPI PATTERN DATE:

08 Jan 2016

VSAPI OPR PATTERN File:

12.261.00

VSAPI OPR PATTERN Date:

09 Jan 2016

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.

  • In 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.exe //B "%User Temp%\{malware name}""
  • In HKEY_LOCAL_MACHINE\Software\MicrosoftWindows\CurrentVersion\Run
    • {malware name} = "wscript.exe //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.
  • {Removable Drive Letter}:\{Available Folder Name}.lnk

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as VBS_JENXCUS.YXH. 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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