WORM_VOBFUS.SMCF

Trend Micro has received multiple samples of this malware from multiple sources, including customer reports and internal sources. This malware has been noted to employ polymorphism in order to prevent early detection. It uses Facebook as a means to propagate. It also downloads information-stealing malware onto the affected system.

To get a one-glance comprehensive view of the behavior of this Worm, refer to the Threat Diagram shown below.

For the related story, you may read the following blog posts:

• Watch Out for WORM_VOBFUS
• What's the Fuss with WORM_VOBFUS?

This worm has been seen to spread on Facebook.

Whenever it drops a folder, it hides the legitimate folder with the same name in order to escape detection.

It downloads a variant of TSPY_BANCOS onto the affected system, which can steal important personal information such as online banking login 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.

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

It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the 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 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.)

It drops the following files:

• {drive letter}:\x.mpeg

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:

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
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}.eu:443/cWWFwy?d
• http://{random number}.{BLOCKED}1.eu:443/cWWFwy/?d
• http://{BLOCKE}D1.{BLOCKED}ecks.net

It saves the files it downloads using the following names:

• %User Profile%\google.com

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

NOTES:

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.