WORM_VOBFUS.SMJA

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}.nl:443/{random}

It saves the files it downloads using the following names:

• %User Profile%\{random file name}.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 then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

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 the same copies of itself it drops in removable drives to mapped network drives.

Trend Micro detects the downloaded file %User Profile%\{random file name}.exe as variants of TSPY_BANCOS, TSPY_FAREIT or WORM_VOBFUS.SMIT. The contents of the downloaded file can be changed at any time by the malware writer.