Analysis by: Nikko Tamana
ALIASES:

Worm.Win32.Vobfus.erns (Kaspersky), Worm:Win32/Vobfus (Microsoft)

 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 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.

  TECHNICAL DETAILS

File Size: 126,976 bytes
File Type: EXE
Initial Samples Received Date: 04 Feb 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 copies of itself into the affected system:

  • %User Profile%\{varying filename}.exe
  • %User Profile%\{random characters}.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} 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
{random characters} = "%User Profile%\{random characters}.exe"

Other System Modifications

This worm adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\WindowsUpdate

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\WindowsUpdate\
AU

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\WindowsUpdate\
AU
NoAutoUpdate = "1"

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSupperHidden = "1"

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

NOTES:

The file name it uses may contain any of the following strings:

  • Passwords
  • Porn
  • runme
  • Secret
  • Sexy

This worm searches for folders in all removable drives then drops copies of itself as {folder name}.exe. It also uses the file names of files with the following extensions:

  • .avi
  • .bmp
  • .doc
  • .gif
  • .jpe
  • .jpg
  • .mp3
  • .mp4
  • .mpg
  • .pdf
  • .png
  • .tif
  • .txt
  • .wav
  • .wma
  • .wmv
  • .xls

It then sets the attribute of the original file or folder to Hidden and System to trick users into thinking that the dropped copy is the legitimate file or folder. It also drops to mapped network drives the same copies of itself as dropped in removable drives.