WORM_VOBFUS.CB

October 08, 2012
 Analysis by: Roland Marco Dela Paz
 ALIASES:

Microsoft : Worm:Win32/Vobfus.gen!E; Sophos : Mal/SillyFDC-I

 PLATFORM:

Windows 2000, XP, 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:

Propagates via removable drives

This worm arrives by connecting affected removable drives to a system. It may be unknowingly downloaded by a user while visiting malicious websites.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size:

237,568 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

19 Jan 2011

Payload:

Compromises system security

Arrival Details

This worm arrives by connecting affected removable drives to a system.

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}.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} = %User Profile%\{random}.exe /{parameter}

Other System Modifications

This worm modifies the following registry entries to hide files with Hidden 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 the following copy(ies) of itself in all removable drives:

  • {random1}.exe
  • {random2}.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 codes}
[auTorUN]
ACTiON=View Files
shellexecute={random1}.exe
;{garbage codes}
icoN=%SyStemrOot%\sYstEM32\SHeLl32.Dll,4
;{garbage codes}
USeautoPLAY=1
;{garbage codes}

Backdoor Routine

This worm opens the following ports:

  • 8000

It connects to the following websites to send and receive information:

  • {BLOCKED}.{BLOCKED}.147.15

As of this writing, the said sites are inaccessible.

Other Details

This worm does the following:

  • It drops the following shortcut files to removable drives:
    • [DRIVE]:\New Folder.lnk
    • [DRIVE]:\Passwords.lnk
    • [DRIVE]:\Documents.lnk
    • [DRIVE]:\Pictures.lnk
    • [DRIVE]:\Music.lnk
    • [DRIVE]:\Video.lnk
  • These files points to its dropped copy in the removable drive. The files then serve as an autostart technique of the malware.

  SOLUTION

Minimum Scan Engine:

8.900

VSAPI PATTERN File:

07.776.18

VSAPI PATTERN Date:

19 Jan 2011

VSAPI PATTERN Date:

1/19/2011 12:00:00 AM

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

Restart in Safe Mode

[ Learn More ]

Step 3

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]:\New Folder.lnk  
[DRIVE]:\Passwords.lnk   
[DRIVE]:\Documents.lnk   
[DRIVE]:\Pictures.lnk    
[DRIVE]:\Music.lnk       
[DRIVE]:\Video.lnk  

Step 4

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} = %User Profile%\{random}.exe /{parameter}

Step 5

Restore this modified 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\Explorer\Advanced
    • From: ShowSuperHidden = 0
      To: ShowSuperHidden = 1

Step 6

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

[ Learn More ]
;{garbage codes}
[auTorUN]
ACTiON=View Files
shellexecute={random1}.exe
;{garbage codes}
icoN=%SyStemrOot%\sYstEM32\SHeLl32.Dll,4
;{garbage codes}
USeautoPLAY=1
;{garbage codes}

Step 7

Scan your computer with your Trend Micro product to delete files detected as WORM_VOBFUS.CB. 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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