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VBS_JENXCUS.A

June 06, 2013
 Analysis by: Alvin Bacani
 ALIASES:

FSecure: Trojan.VBE.Agent.C

 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:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware, Propagates via removable drives


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 creates registry entries to enable its automatic execution at every system startup.

It disables Task Manager, Registry Editor, and Folder Options. It modifies certain registry entries to hide file extensions.

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

It modifies certain registry entries to hide Hidden files.

  TECHNICAL DETAILS

File Size:

4,426 bytes

File Type:

VBS

Memory Resident:

Yes

Initial Samples Received Date:

27 May 2013

Payload:

Connects to URLs/IPs, Collects system information

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 drops the following copies of itself into the affected system:

  • %User Temp%\Serviec.vbe

(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
Serviec.vbe = "%USER TEMP%"\Serviec.vbe

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Serviec.vbe = "%USER TEMP%"\Serviec.vbe

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

  • %User Startup%\Serviec.vbe

(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 creates the following registry entry(ies) to disable Task Manager, Registry Tools and Folder Options:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\Currentversion\Policies\
Explorer
NoFolderOptions = "1"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\Currentversion\Policies\
Explorer
NoFolderOptions = "1"

It modifies the following registry entries to hide file extensions:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\Currentversion\Explorer\
Advanced
HideFileExt = "1"

(Note: The default value data of the said registry entry is 0.)

Propagation

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

  • Serviec.vbe

Backdoor Routine

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

  • exc- execute the command supplied by the server
  • uns - exits session

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

  • t{BLOCKED}pionking.{BLOCKED}p.org via 1604

It posts the following information to its command and control (C&C) server:

  • volume serial number
  • computer name
  • current username
  • operating system
  • process id
  • antivirus
  • firewall
  • country

Other Details

This worm modifies the following registry entries to hide Hidden files:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\Currentversion\Explorer\
Advanced
Hidden = "0"

(Note: The default value data of the said registry entry is 1.)

NOTES:

It disables Folder Options.

It drops shortcut files pointing to the copy of itself in removable drives. These dropped .LNK files use the names of the files located on the said drives for their file names. It then sets the attributes of the original folders to Hidden to trick the user into clicking the .LNK files. When the .LNK has been executed it will trigger execution of the malware Serviec.vbe.

The .LNK files are detected as LNK_JENXCUS.SM.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.948.02

FIRST VSAPI PATTERN DATE:

29 May 2013

VSAPI OPR PATTERN File:

9.949.00

VSAPI OPR PATTERN Date:

29 May 2013

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

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%\Serviec.vbe
  • %User Startup%\Serviec.vbe

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
    • Serviec.vbe = "%User Temp%"\Serviec.vbe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Serviec.vbe = "%User Temp%"\Serviec.vbe

Step 5

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\Policies\Explorer
    • NoFolderOptions = "1"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Currentversion\Policies\Explorer
    • NoFolderOptions = "1"

Step 6

Restore this modified registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator’s help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\Currentversion\Explorer\Advanced
    • From: Hidden = 0
      To: Hidden = 1
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\Currentversion\Explorer\Advanced
    • From: HideFileExt = 1
      To: HideFileExt = 0

Step 7

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