TROJ_ROOTKIT.H

Malware type: Trojan

Aliases: Trojan-Spy.Win32.Zagaban.a (Kaspersky), Generic.cb (McAfee), TR/Spy.Zagaban.A (Avira),

In the wild: Yes

Destructive: No

Language: English

Platform: Windows NT, 2000, XP

Encrypted: No

Overall risk rating:

Reported infections:

Damage potential:

Medium

Distribution potential:

Low

Description: 

This Trojan tool may be installed on a system either by another malicious program or by a remote malicious user upon gaining access to a target system.

It is used by several malware, particularly WORM_RBOT and WORM_SDBOT variants, to hide their processes.

For additional information about this threat, see:

Description created: Jan. 14, 2005 6:31:46 AM GMT -0800
Description updated: Feb. 20, 2005 1:04:03 AM GMT -0800


TECHNICAL DETAILS


File type: PE

Memory resident:  Yes

Size of malware: 6,656 Bytes

Initial samples received on: Dec 19, 2004

Payload 1: Hides processes

Details:

This Trojan tool may be installed on a system either by another malicious program or by a remote malicious user upon gaining access to a target system.

It adds the following registry entry to ensure that it executes at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
AV UpDate = "%System%\Spool\prtprocs\Update.exe"

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

It may also drop a copy of itself as the file MSDIRECTX.SYS in the Windows system folder.

It then registers itself as a service named msdirectx by creating the following registry key and entry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\msdirectx
DisplayName = "msdirectx"

It is used by several malware, particularly WORM_RBOT and WORM_SDBOT variants, to hide their processes.

ThisTrojan runs on Windows NT, 2000, XP, and Server 2003.

Analysis By: Steve Inosanto Espino

Updated By: Juan Cesar Cuevas

Revision History:

First pattern file version: 2.308.08
First pattern file release date: Dec 19, 2004
 
Jul 3, 2005 - Modified Virus Report
Sep 14, 2005 - Modified Virus Report

SOLUTION


Minimum scan engine version needed: 6.810

Pattern file needed: 2.636.07

Pattern release date: May 19, 2005


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:

AUTOMATIC REMOVAL INSTRUCTIONS

MANUAL REMOVAL INSTRUCTIONS

Restarting in Safe Mode

On Windows NT (VGA mode)

  1. Click Start>Settings>Control Panel.
  2. Double-click the System icon.
  3. Click the Startup/Shutdown tab.
  4. Set the Show List field to 10 seconds and click OK to save this change.
  5. Shut down and restart your computer.
  6. Select VGA mode from the startup menu.

On Windows 2000

  1. Restart your computer.
  2. Press the F8 key, when you see the Starting Windows bar at the bottom of the screen.
  3. Choose the Safe Mode option from the Windows Advanced Options Menu then press Enter.

On Windows XP

  1. Restart your computer.
  2. Press F8 after the Power-On Self Test (POST) is done. If the Windows Advanced Options Menu does not appear, try restarting and then pressing F8 several times after the POST screen.
  3. Choose the Safe Mode option from the Windows Advanced Options Menu then press Enter.

Disabling Malware Service

This stops the running malware service on systems running Windows NT, 2000, and XP.

  1. Open a command prompt window. Click Start>Run, type CMD, and then press the Enter.
  2. At the command prompt, type the following:
    NET STOP "MSDIRECTX"
  3. Press Enter. A message should indicate that the service has been stopped successfully.
  4. Close the command prompt window.

Editing the Registry

This malware modifies the system'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 NT 4.0
  2. HOW TO: Back Up, Edit, and Restore the Registry in Windows XP
  3. HOW TO: Backup, Edit, and Restore the Registry in Windows 2000

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:
    AV UpDate = "%System%\Spool\prtprocs\Update.exe"
    (Note: %System% is the Windows system folder, which is usually C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and 2003.)
  4. In the left panel, locate and delete the subkey:
    HKEY_LOCAL_MACHINE>SYSTEM>CurrentControlSet>Services>
    msdirectx
  5. Close Registry Editor.

Important Windows XP Cleaning Instructions

Users running Windows XP must disable System Restore to allow full scanning of infected systems.

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

Running Trend Micro Antivirus

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

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




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