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WORM_DELF.BRF

Overview

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:

Medium

Distribution potential:

Medium

Infection Channel 1 : Propagates via removable drives


Description: 

Upon execution, this worm drops a copy of itself as WINCFGS.EXE in the Windows system folder. It also drops and executes the Chinese version of NOTEPAD.EXE, KB20060111.EXE, in the Windows folder.

Whenever a USB device is plugged onto an affected machine, this worm drops a copy of itself in the following path:

    {USB drive letter}\RECYCLER\RECYCLER\autorun.exe

If the path, {USB drive letter}\RECYCLER\RECYCLER does not exist, this worm creates it.

This worm also creates the file {USB drive letter}\AUTORUN.INF, which is responsible in automatically executing AUTORUN.EXE whenever a USB device is plugged on the affected machine.

For additional information about this threat, see:

Description created: Jun. 29, 2006 4:06:47 AM GMT -0800


Technical Details

File type: PE

Memory resident:  Yes

Size of malware: 47,104 Bytes (compressed); 1,069,568 Bytes (uncompressed)

Initial samples received on: Jun 27, 2006

Compression type: UPX

Payload 1: Drops files (Chinese version of NOTEPAD.EXE)

Details:

Installation and Autostart

Upon execution, this worm drops a copy of itself as WINCFGS.EXE in the Windows system folder. It also drops and executes the Chinese version of NOTEPAD.EXE, KB20060111.EXE, in the Windows folder.

It modifies the following registry entry to ensure its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Windows
Load = "%System%\WINCFGS.EXE"

(Note: The default value data of the said entry is null.)

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Propagation Routine

Whenever a USB device is plugged onto an affected machine, this worm drops a copy of itself in the following path:

    {USB drive letter}\RECYCLER\RECYCLER\autorun.exe

If the path, {USB drive letter}\RECYCLER\RECYCLER does not exist, this worm creates it.

This worm also creates the file {USB drive letter}\AUTORUN.INF, which contains the following lines in its body:

[autorun]
open=.\RECYCLER\RECYCLER\autorun.exeshell\1=Open
shell\1\Command=.\RECYCLER\RECYCLER\autorun.exe
shell\2\=Browser
shell\2\Command=.\RECYCLER\RECYCLER\autorun.exe
shellexecute=.\RECYCLER\RECYCLER\autorun.exe

The aforementioned file is responsible in automatically executing AUTORUN.EXE whenever a USB device is plugged on the affected machine.

Other Details

This worm creates the following mutex to ensure that only one instance of itself is running in the memory:

USBSpyRunMutex

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

Analysis By: Jonathan N. San Jose

Revision History:

First pattern file version: 3.532.03
First pattern file release date: Jun 27, 2006

Solution

Minimum scan engine version needed: 7.500

Pattern file needed: 3.749.00

Pattern release date: Sep 13, 2006


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:

Terminating the Malware Program

This procedure terminates the running malware process.

  1. Open Windows Task Manager.
    • On Windows 98 and ME, press
    CTRL+ALT+DELETE
    • On Windows NT, 2000, XP, and Server 2003, press
    CTRL+SHIFT+ESC, then click the Processes tab.
  2. In the list of running programs*, locate the process:
    wincfgs.EXE
  3. Select the malware process, then press either the End Task or the End Process button, depending on the version of Windows on your computer.
  4. To check if the malware process has been terminated, close Task Manager, and then open it again.
  5. Close Task Manager.

*NOTE: On computers running Windows 98 and ME, Windows Task Manager may not show certain processes. You can use a third party process viewer such as Process Explorer to terminate the malware process.

On computers running all Windows platforms, if the process you are looking for is not in the list displayed by Task Manager or Process Explorer, continue with the next solution procedure, noting additional instructions. If the malware process is in the list displayed by either Task Manager or Process Explorer, but you are unable to terminate it, restart your computer in safe mode.

Editing the Registry

This malware modifies the computer's registry. Users affected by this malware may need to modify or delete specific registry keys or entries. For detailed information regarding registry editing, please refer to the following articles from Microsoft:

  1. HOW TO: Backup, Edit, and Restore the Registry in Windows 95, Windows 98, and Windows ME
  2. HOW TO: Backup, Edit, and Restore the Registry in Windows NT 4.0
  3. HOW TO: Backup, Edit, and Restore the Registry in Windows 2000
  4. HOW TO: Back Up, Edit, and Restore the Registry in Windows XP and Server 2003

Removing Autostart Entry from the Registry

Removing autostart entries from the registry prevents the malware from executing at startup.

If the registry entry below is not found, the malware may not have executed as of detection. If so, proceed to the succeeding solution set.

  1. Open Registry Editor. Click Start>Run, type REGEDIT, then press Enter.
  2. In the left panel, double-click the following:
    HKEY_CURRENT_USER>Software>Microsoft>
    Windows NT>CurrentVersion>Windows
  3. In the right panel, locate the entry:
    load = "%System%\WINCFGS.EXE"
    (Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, and C:\Windows\System32 on Windows XP and Server 2003.)
  4. Right-click on this registry entry and choose Modify. Change the value of this entry to:
    load = ""
  5. Close Registry Editor.

Deleting the Malware File

  1. Right-click Start then click Search... or Find..., depending on the version of Windows you are running.
  2. In the Named input box, type:
    KB20060111.exe
  3. In the Look In drop-down list, select the drive that contains Windows, then press Enter.
  4. Once located, select the file then press SHIFT+Delete.
  5. Locate and delete the file AUTORUN.INF in all removable drives.

Important Windows ME/XP Cleaning Instructions

Users running Windows ME and XP must disable System Restore to allow full scanning of infected computers.

Users running other Windows versions can proceed with the succeeding solution set(s).

Running Trend Micro Antivirus

If you are currently running in safe mode, please restart your computer normally before performing the following solution.

Scan your computer with Trend Micro antivirus and delete files detected as WORM_DELF.BRF. To do this, Trend Micro customers must download the latest virus pattern file and scan their computer. Other Internet users can use HouseCall, the Trend Micro online virus scanner.




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