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WORM_VOBFUS.SML

November 28, 2012
 Analysis by: kathleenno
 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

Infection Channel:

Propagates via removable drives


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.

  TECHNICAL DETAILS

File Size:

Varies

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

08 Mar 2011

Installation

This worm drops the following copies of itself into the affected system:

  • %User Profile%\{random filename}.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 filename} = %User Profile%\{random filename}.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]
{garbage characters}
actiOn=
{garbage characters}
open=SOAzuom.EXe
{garbage characters}
icOn=hnG.ico
{garbage characters}
USEauTOPLaY=1
{garbage characters}

NOTES:
It 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 random file names, names of the existing folders, and hardcoded file names. This enables the copy of the worm to execute first before opening the real folder. It then changes the attributes of the original folders to Hidden and System to avoid early detection.

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

7.886.12

FIRST VSAPI PATTERN DATE:

08 Mar 2011

VSAPI OPR PATTERN File:

7.911.00

VSAPI OPR PATTERN Date:

19 Mar 2011

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

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

Step 3

Restart in Safe Mode

[ Learn More ]

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 filename} = %User Profile%\{random filename}.exe

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: 1

Step 6

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

[ Learn More ]
{garbage characters}
[autorun]
{garbage characters}
actiOn=
{garbage characters}
open=SOAzuom.EXe
{garbage characters}
icOn=hnG.ico
{garbage characters}
USEauTOPLaY=1
{garbage characters}

Step 7

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