VBS_JENXCUS.BI

 Analysis by: Mark Joseph Manahan

 ALIASES:

Worm:VBS/Jenxcus.BB (Microsoft), VBS/Kryptik.Y trojan (Eset), Backdoor.Trojan (Symantec)

 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:
 INFORMATION EXPOSURE:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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.

  TECHNICAL DETAILS

File Size:

581,288 bytes

File Type:

VBS

Memory Resident:

Yes

Initial Samples Received Date:

12 Nov 2013

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:

  • %Application Data%\{malware name}.vbs
  • %User Startup%\{malware name}.vbs

(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 and 7.. %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.)

Autostart Technique

This worm adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{malware name} = "wscript //B "%Application Data%\{malware name}.vbs"

Other System Modifications

This worm adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\{malware name}

Other Details

This worm connects to the following possibly malicious URL:

  • {BLOCKED}d.{BLOCKED}p.biz:81