Analysis by: Sabrina Lei Sioting
 Modified by: Sabrina Sioting
 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

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

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: 1,519,616 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 01 Jun 2011

Arrival Details

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

Installation

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

  • %User Profile%\Application Data\vfbu.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.)

It is injected into the following processes running in memory:

  • explorer.exe

Autostart Technique

This worm adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Taskman = "%User Profile%\Application Data\vfbu.exe"

Propagation

This worm creates the following folders in all removable drives:

  • U3ROM

It drops the following copy(ies) of itself in all removable drives:

  • U3ROM\system32.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}
[autorun]
open=U3ROM/system32.exe
;{garbage}
icon=U3ROM/default.ico
;{garbage}
action=Open
;{garbage}
shell\open\command=U3ROM/system32.exe
shell\explore\command=U3ROM/system32.exe
useautoplay=1
:GOTO NUL
;{garbage}

NOTES:
It drops the following files in all removable drives:

  • U3ROM\default.ico

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 8.196.07
FIRST VSAPI PATTERN DATE: 01 Jun 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_OTORUN.GK

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • Taskman = %User Profile%\Application Data\vfbu.exe

Step 5

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %Drive letter%\U3ROM

Step 6

Search and delete AUTORUN.INF files created by WORM_OTORUN.GK that contain these strings

[ Learn More ]


;{garbage}
[autorun]
open=U3ROM/system32.exe
;{garbage}
icon=U3ROM/default.ico
;{garbage}
action=Open
;{garbage}
shell\open\command=U3ROM/system32.exe
shell\explore\command=U3ROM/system32.exe
useautoplay=1
:GOTO NUL
;{garbage}

Step 7

Scan your computer with your Trend Micro product to delete files detected as WORM_OTORUN.GK. 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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