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WORM_VOBFUS.USRP

May 08, 2014
 Analysis by: Al Victor de Leon
 ALIASES:

Trojan horse Inject2.ABUM (AVG), Worm.Win32.Vobfus.esah (Kaspersky), Worm:Win32/Vobfus.ZS (Microsoft), W32/FakeFolder.V.worm (Panda)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


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.

  TECHNICAL DETAILS

File Size:

147,456 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

28 Apr 2014

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 files:

  • {removable drive letter}:\x.mpeg

It drops the following copies of itself into the affected system:

  • %User Profile%\{random file name 1}.exe
  • %User Profile%\{random folder name}\{random file name 2}.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
{random} = "%User Profile%\{random folder name}\{random file name 2}.exe /{random character}"

It drops the following shortcut pointing to its copy in the User Startup folder to enable its automatic execution at every system startup:

  • %Start Menu%\Programs\Startup\{random file name 3}.lnk

(Note: %Start Menu% is the current user's Start Menu folder, which is usually C:\Windows\Start Menu or C:\Documents and Settings\{User name}\Start Menu on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu on Windows Vista and 7.)

Other System Modifications

This worm adds the following registry entries as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\WindowsUpdate\
AU
NoAutoUpdate = "1"

It 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:

  • {removable drive letter}:\{random file name 2}.exe
  • {removable drive letter}:\I love you.exe
  • {removable drive letter}:\Naked.exe
  • {removable drive letter}:\Password.exe
  • {removable drive letter}:\Sexy.exe
  • {removable drive letter}:\Webcam.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:

[autorun]
open={random file name 2}.exe
action={random number}
useautoplay=1

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.14.170:7112
  • {BLOCKED}1.{BLOCKED}0.com

NOTES:

The malware drops the following shortcut files to removable drives (pointing to dropped file):

  • {removable drive letter}:\Favourites.lnk
  • {removable drive letter}:\Movies.lnk
  • {removable drive letter}:\Music.lnk
  • {removable drive letter}:\Passwords.lnk
  • {removable drive letter}:\Pictures.lnk
  • {removable drive letter}:\Private.lnk
  • {removable drive letter}:\Search.lnk
  • {removable drive letter}:\Secret Folder.lnk

The malware drops copies of itself in the removable drive and uses the names of the folder(s) and file(s) located on the said drives.

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

10.760.02

FIRST VSAPI PATTERN DATE:

29 Apr 2014

VSAPI OPR PATTERN File:

10.761.00

VSAPI OPR PATTERN Date:

29 Apr 2014

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Restart in Safe Mode

[ Learn More ]

Step 3

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 folder name}\{random file name 2}.exe /{random character}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU
    • NoAutoUpdate = "1"

Step 4

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 5

Search and delete these files

[ Learn More ]
There may be some 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.
  • %Start Menu%\Programs\Startup\{random file name 3}.lnk
  • {removable drive letter}:\x.mpeg
  • {removable drive letter}:\Favourites.lnk
  • {removable drive letter}:\Movies.lnk
  • {removable drive letter}:\Music.lnk
  • {removable drive letter}:\Passwords.lnk
  • {removable drive letter}:\Pictures.lnk
  • {removable drive letter}:\Private.lnk
  • {removable drive letter}:\Search.lnk
  • {removable drive letter}:\Secret Folder.lnk

Step 6

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

[ Learn More ]
[autorun]
open={random file name 2}.exe
action={random number}
useautoplay=1

Step 7

  1. Open a command prompt.
    • For Windows 2000, Windows XP, and Windows Server 2003 users, click Start>Run. In the Search box, type CMD then press Enter.
    • For Windows Vista and Windows 7 users, click Start, type CMD in the Search input field then press Enter.
  2. In the CMD console, type the following:

    ATTRIB [+R | -R] [+A | -A ] [+S | -S] [+H | -H] [+I | -I] [drive:][path][file name] [/S [/D] [/L]]

    Where:
    + Sets an attribute.
    - Clears an attribute
    R Read-only file attribute
    A Archive file attribute
    S System file attribute
    H Hidden file attribute
    I Not content indexed file attribute
    [drive:][path][filename]
    Specifies a file or files for attrib to process
    /S Processes matching files in the current folder and all subfolders.
    /D Processes folders
    /L Work on the attributes of the Symbolic Link versus the target of the Symbolic Link
    Example:
    To unhide all files and folders (including subfolders) in drive D:
    ATTRIB –H D:\* /S /D
  3. Repeat Step 3 for folders and files in other drives or directories.

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_VOBFUS.USRP. 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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