Analysis by: kathleenno
ALIASES:

VBObfus.g (Mcafee); Troj/VBObfus-C (Sophos)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • 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.

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.

  TECHNICAL DETAILS

File Size: 131,072 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 20 Jul 2011

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%\{random file name}.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

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} = %User Profile%\{random file name}.exe

Other System Modifications

This worm 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 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:

{garbage characters}
[autorun]
ICON={random file name}.ico
{garbage characters}
open={random file name}.eXE
{garbage characters}
ACtIOn=5342
{garbage characters}
usEAUtoPLay=1
{garbage characters}

Other Details

This worm attempts to access the following websites to download files, which are possibly malicious:

  • ns1.{BLOCKED}1532.com

NOTES:
This malware drops .LNK files in removable drives that point to a copy of itself. This is done to automatically execute dropped copies when the said drives are accessed. These .LNK files use the following file names:

  • Documents.lnk
  • Music.lnk
  • New Folder.lnk
  • Passwords.lnk
  • Pictures.lnk
  • Video.lnk

It also uses the names of existing folders and names of files with the following extensions:

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

This routine enables the copy of the worm to execute first before opening the real folder or file. It then changes the attributes of the original folders and files to Hidden and System to avoid early detection. It also adds the following non-malicious files in removable drives:

  • {random filename}.ico
  • x.mpeg