WORM_VBNA.SM

This worm may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.

It modifies registry entries to hide files with System and Read-only attributes.

It drops copies of itself in all removable drives. 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 may be dropped by other malware.

It may be unknowingly downloaded by a user while visiting malicious websites.

Installation

This worm drops the following copies of itself into the affected system:

• %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.)

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
{Malware File Name} = %User Profile%\{Random File Name}.exe

Other System Modifications

This worm 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 copies of itself in all removable drives.

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:

[aUToRUN]
aCtioN=Open folder to view files
SHELLexeCUtE= {Random File Name}.eXE
ICOn=%sYsTEMRoOt%\SYSTEm32\sHelL32.DlL,4
USeAutoPLAy=1

Other Details

Based on analysis of the codes, it has the following capabilities:

• This worm searches for folders on removable drives and create shortcut files on these drives using the folder names as its filename to execute its dropped copy. It then hides the folders found.
• This worm also drops link files (.LNK files) with random file names in removable drives. The said .LNK file are detected by Trend Micro as LNK_STUXNET.SM. It also drops the file xxx.dll on removable drives detected by Trend Micro as WORM_VOBFUS.AI.