WORM_VOBFUS.OK

This worm arrives by connecting affected removable drives to a system. 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 modifies registry entries to hide files with System and Read-only attributes.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

Arrival Details

This worm arrives by connecting affected removable drives to a system.

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 files:

• {drive letter}:\x.mpeg

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

• %User Profile%\{random file name}.exe
• %User Profile%\Passwords.exe
• %User Profile%\Porn.exe
• %User Profile%\Secret.exe
• %User Profile%\Sexy.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 file name}.exe = "%User Profile%\{random file name}.exe /{random character}"

Other System Modifications

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

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

It modifies the following registry entries to hide files with System and Read-only attributes:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = 0

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

Propagation

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

• {drive letter}:\{random file name}.exe
• {drive letter}:\Passwords.exe
• {drive letter}:\Porn.exe
• {drive letter}:\Secret.exe
• {drive letter}:\Sexy.exe
• {drive letter}:\{folder name}.exe

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

{garbage characters}
[autorun]
{garbage characters}
open={random}.eXE
{garbage characters}
ACTION={random number}
UseautopLAY=1
{garbage characters}

Download Routine

This worm accesses the following websites to download files:

• http://{random number}.{BLOCKED}x.eu:443/cWWFwy?d

It saves the files it downloads using the following names:

• %User Profile%\google.com

NOTES:

It searches for .rar files with .exe file inside it. If it finds one, it will drop a copy of itself inside with the following file names:

• Passwords.exe
• Porn.exe
• Secret.exe
• Sexy.exe

It searches for folders in all removable drives then drops copies of itself as {folder name}.exe.

It uses the filenames 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 folder to Hidden and System to trick users into thinking that the dropped copy is the legitimate folder.

It also drops to mapped network drives the same copies of itself as dropped in removable drives.

Trend Micro detects the downloaded file %User Profile%\google.com as variants of TSPY_BANCOS. The contents of the downloaded file can be changed at any time by the malware writer.