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Threat Encyclopedia

WORM_VOBFUS.SMAY

ANALYSIS BY

Rika Joi Gregorio


ALIASES:

Worm:Win32/Vobfus.LZ (Microsoft), Worm.Win32.Vobfus (Ikarus), Worm.Win32.VBNA.bb (Sunbelt)

PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type:Worm

  • Destructiveness:No

  • Encrypted: Yes

  • In the wild: Yes

OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware, Propagates via flashdrives, Propagates via shared drives


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.

TECHNICAL DETAILS

File Size:

200,704 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

22 Nov 2012

Payload:

Connects to URLs/IPs, Downloads files

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:

  • {BLOCKED}1.{BLOCKED}dater.net
  • http://{BLOCKED}6.{BLOCKED}1.eu:443/YfCNaFR?f

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.

SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.542.04

FIRST VSAPI PATTERN DATE:

22 Nov 2012

VSAPI OPR PATTERN File:

9.543.00

VSAPI OPR PATTERN Date:

23 Nov 2012

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Remove malware files dropped/downloaded by WORM_VOBFUS.SMAY

  • TSPY_BANCOS

Step 3

Scan your computer with your Trend Micro product and note files detected as WORM_VOBFUS.SMAY

Step 4

Restart in Safe Mode

[ Learn More ]

Step 5

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.


  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {random file name} = "%User Profile%\{random file name}.exe /{random character}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU
    • NoAutoUpdate = "1"

Step 6

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.


  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: ShowSuperHidden = "0"
      To: ShowSuperHidden = "1"

Step 7

Search and delete AUTORUN.INF files created by WORM_VOBFUS.SMAY that contain these strings

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

Step 8

Search and delete this file

[ Learn More ]
There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files and folders in the search result.
  • {drive letter}:\x.mpeg

Step 9

Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_VOBFUS.SMAY. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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