WORM_VB.CBW

Malware type: Worm

Aliases: Worm.Win32.VB.gp (Kaspersky), W32/USBAgent (McAfee), W32.SillyFDC (Symantec), TR/Crypt.CFI.Gen (Avira),

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:

Low

Distribution potential:

Medium

Infection Channel 1 : Propagates via removable drives


Infection Channel 2 : Copies itself in all available physical drives


Description: 

This memory-resident worm propagates by dropping a copy of itself as TEL.XLS.EXE into removable drives and all available physical drives. It also drops the file named AUTORUN.INF together with a copy of itself. The said .INF file enables the dropped copy to automatically execute once a user accesses the affected drives.

It also modifies a certain registry entry to hide files with the Hidden attributes. As a result, files with the said attribute are not displayed when viewed via Windows Explorer.

For additional information about this threat, see:

Description created: Jan. 8, 2007 6:16:16 PM GMT -0800


TECHNICAL DETAILS


File type: PE

Memory resident:  Yes

Size of malware: Varies

Initial samples received on: Dec 20, 2006

Payload 1: Hides files with certain attributes

Details:

Installation and Autostart Technique

Upon execution, this worm drops the following copies of itself into the Windows system folder:

  • algsrv.exe
  • FileKan.exe
  • SocksA.exe

It then creates the following registry entries to ensure its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\
CurrentVersion\Run
ASocksrv = "SocksA.exe"

HKEY_CURRENT_USER\Software\Microsoft\Windows\
CurrentVersion\Run
BSserver = "FileKan.exe"

It also modifies the following registry entry as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\SHOWALL
CheckedValue = "0"

(Note: This worm also modifies the registry entry type from DWORD to SZ. The default value data for this registry entry is 1. Modifying the said registry entry to 0 hides files with the Hidden attribute when viewed with Windows Explorer. Restoring it to 1 displays said files.)

Propagation via Removable Drives and All Physical Drives

This worm propagates by dropping a copy of itself as TEL.XLS.EXE into removable drives and all available physical drives. It also drops the file named AUTORUN.INF together with a copy of itself. This .INF file contains the following code:

[AutoRun]
open=tel.xls.exe
shellexecute=tel.xls.exe
shell\Auto\command=tel.xls.exe
shell\Auto
explorer.exe
tel.xls.exe

This file enables the dropped copy to automatically execute once a user accesses the affected drives.

Affected Platforms

This worm affects systems running on Windows 98, ME, NT, 2000, XP, and Server 2003.

Analysis By: Alvin Jethro Calderon Bacani

Revision History:

First pattern file version: 4.128.01
First pattern file release date: Dec 20, 2006
 
May 14, 2007 - Modified Malware Report
May 17, 2007 - Modified Malware Report

SOLUTION


Minimum scan engine version needed: 8.000

Pattern file needed: 4.640.03

Pattern release date: Aug 8, 2007


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:

Identifying the Malware Program

To remove this malware, first identify the malware program.

  1. Scan your computer with your Trend Micro antivirus product.
  2. NOTE the path and file name of all files detected as WORM_VB.CBW.

Trend Micro customers need to download the latest virus pattern file before scanning their computer. Other users can use Housecall, the Trend Micro online virus scanner.

Terminating the Malware Program

This procedure terminates the running malware process. You will need the name(s) of the file(s) detected earlier.

If the process you are looking for is not in the list displayed by Task Manager, proceed to the succeeding solution set.

  1. Open Windows Task Manager.
    • On Windows 95, 98, and ME, press
    CTRL%20ALT%20DELETE
    • On Windows NT, 2000, XP, and Server 2003, press
    CTRL%20SHIFT%20ESC, then click the Processes tab.
  2. In the list of running programs*, locate the malware file(s) detected earlier.
  3. Select one of the detected files, then press either the End Task or the End Process button, depending on the version of Windows on your computer.
  4. Do the same for all detected malware files in the list of running processes.
  5. To check if the malware process has been terminated, close Task Manager, and then open it again.
  6. Close Task Manager.

*NOTE: On computers running Windows 95, 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 Entries from the Registry

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

If the registry entries below are 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_LOCAL_MACHINE>SOFTWARE>Microsoft>
    Windows>CurrentVersion>Run
  3. In the right panel, locate and delete the entry:
    ASocksrv = "SocksA.exe"
  4. In the left panel, double-click the following:
    HKEY_CURRENT_USER>Software>Microsoft>
    Windows>CurrentVersion>Run
  5. In the right panel, locate and delete the entry:
    BSserver = "FileKan.exe"

Restoring Modified Entry in the Registry

  1. Still in the Registry Editor, in the left panel, double-click the following:
    HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>
    Windows>CurrentVersion>Explorer>
    Advanced>Folder>Hidden>SHOWALL
  2. In the right panel, locate and delete the following entry:
    CheckedValue = "0"
  3. Still in the right panel, right-click and choose New. Click on DWORD Value.
  4. Type the following as its entry name:
    CheckedValule
  5. Double-click on the created entry. Change the value data to:
    1
  6. Close Registry Editor.

Deleting AUTORUN.INF

  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:
    AUTORUN.INF
  3. In the Look In drop-down list, select a drive, then press Enter.
  4. Select the file, then open using Notepad.
  5. Check if the following lines are present in the file:
    open=tel.xls.exe
    shellexecute=tel.xls.exe
    shell\Auto\command=tel.xls.exe
    shell\Auto
    explorer
    tel.xls.exe
  6. If the lines are present, delete the file.
  7. Repeat steps 3 to 6 for AUTORUN.INF files in the remaining removable drives.
  8. Close Search Results.

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_VB.CBW. 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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