Threat Encyclopedia

WORM_VOBFUS.AI

Malware type: Worm

Aliases: No Alias Found

In the wild: Yes

Destructive: No

Language: English

Platform: Windows 98, ME, NT, 2000, XP, Server 2003

Encrypted: No

Overall risk rating:

Reported infections:

Damage potential:

Low

Distribution potential:

Medium

Infection Channel 1 : Propagates via removable drives


Description: 

This worm may be downloaded from certain remote sites.

It creates registry entries to enable its automatic execution at every system startup.

It modifies registry entries to hide files with both System and Read-only attributes. It lowers the security setting of Internet Explorer.

It drops copies of itself in all removable drives. It drops an AUTORUN.INF file to automatically execute dropped copies when the drives are accessed.

It drops component files.

For additional information about this threat, see:

Description created: Jul. 24, 2010 11:30:57 AM GMT -0800


TECHNICAL DETAILS


File type: PE

Memory resident:  Yes

Size of malware: 113,664 Bytes

Initial samples received on: Jul 24, 2010

Related toEXPL_CPLNK.SM

Payload 1: Drops files

Payload 2: Downloads files

Details:

Arrival Details

This worm may be downloaded from the following remote site(s):

  • http://{BLOCKED}nline.net:999/a

Autostart Techniques

This worm creates the following registry entry(ies) 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 entry(ies) to hide files with both System and Read-only attributes:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = "0"

(Note: The default value data for the said registry entry is 1.)

It lowers the security setting of Internet Explorer.

Propagation via Removable Drives

This worm drops copies of itself in all removable drives.

It drops an AUTORUN.INF file to automatically execute dropped copies when the drives are accessed.

The said .INF file contains the following strings:

[aUToRun]
action=Open folder to view files
sHELLexECUtE={Malware File Name}.exe
icoN=%systEmROOt%\sYStem32\shell32.dlL,4
uSeAutOPlay=1

Dropping Routine

This worm drops the following component file(s):

  • %User Profile%\4x.exe - detected as TROJ_MUFANOM.AO

(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. )

It drops the following files:

  • {removable drive}:\{3-Random Letters}.dll - detected as WORM_VOBFUS.AI
  • {removable drive}:\z{random characters}.lnk - detected as EXPL_CPLNK.SM

It drops .LNK files that reference a copy of itself and the dropped .DLL file in removable drives. These dropped files use the names of the folders located on the said drives for their filenames. It then hides the original folders to further fool the users.

In addition, it also uses the following names:

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

The dropped .LNK files are detected by Trend Micro as EXPL_CPLNK.SM.

Download Routine

This worm access the following remote site to download an updated copy of itself:

  • http://{BLOCKED}nline.net:999/a

It saves the downloaded copy as follows:

  • %User Profile%\alg.exe

Other Details

This worm also attempts to query the following host name:

  • {BLOCKED}hi.net

Affected Platforms

This worm runs on Windows 98, ME, NT, 2000, XP, and Server 2003.


Analysis By: Michael Cabel

Revision History:

First pattern file version: 7.334.11
First pattern file release date: Jul 24, 2010

SOLUTION


Minimum scan engine version needed: 8.900

Pattern file needed: 8.273.00

Pattern release date: Jul 7, 2011


Important note: The "Minimum scan engine" refers to the earliest Trend Micro scan engine version guaranteed to detect this threat. However, Trend Micro strongly recommends that you update to the latest version in order to get comprehensive protection. Download the latest scan engine here.

Solution:

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

 Step 1: Remove malware files related to WORM_VOBFUS.AI  

 Step 2: Identify and terminate files detected as WORM_VOBFUS.AI  [learn how]

*Note:

  1. For Windows 98 and ME users, Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

 Step 3:  Delete this registry value  [learn how]

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

 Step 4:  Restore this modified registry value  [learn how]

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\Explorer\
    Advanced
    • From: ShowSuperHidden = "0"
      To: ShowSuperHidden = "1"

 Step 5: Search and delete AUTORUN.INF files created by WORM_VOBFUS.AI that contain these strings  [learn how]


[aUToRun]
action=Open folder to view files
sHELLexECUtE={Malware File Name}.exe
icoN=%systEmROOt%\sYStem32\shell32.dlL,4
uSeAutOPlay=1

 Step 6: Scan your computer with your Trend Micro product to delete files detected as WORM_VOBFUS.AI and TROJ_MUFANOM.AO  

*Note: 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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