Analysis by: Mark Joseph Manahan
ALIASES:

Backdoor.Win32.Gulpix (Ikarus), Backdoor.Win32.Gulpix.tz (Kaspersky), BDS/Gulpix.tz (Antivir)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This backdoor may be dropped by other malware.

  TECHNICAL DETAILS

File Size: 290,369 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 22 Nov 2013

Arrival Details

This backdoor may be dropped by other malware.

Installation

This backdoor adds the following folders:

  • %All Users Profile%\DRM
  • %All Users Profile%\DRM\WLM

(Note: %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.)

It adds the following possibly malicious files or file components:

  • %All Users Profile%\DRM\WLM\otf
  • %All Users Profile%\DRM\WLM\TMAS_WLMHook.dll
  • %All Users Profile%\DRM\WLM\TMAS_WLMHook.dll.EMS
  • %All Users Profile%\DRM\WLM\TMAS_WLMMon.exe

(Note: %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.)

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\WLM

HKEY_CURRENT_USER\Software\Nektra

It adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Windows Live Mail
Frameless = "0"

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}b.{BLOCKED}rp.com

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 10.426.03
FIRST VSAPI PATTERN DATE: 22 Nov 2013
VSAPI OPR PATTERN File: 10.427.00
VSAPI OPR PATTERN Date: 23 Nov 2013

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Restart in Safe Mode

[ Learn More ]

Step 3

Delete this registry key

[ 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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • WLM
  • In HKEY_CURRENT_USER\Software
    • Nektra

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 Live Mail
    • Frameless = "0"

Step 5

Search and delete these files

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.  
  • %All Users Profile%\DRM\WLM\otf
  • %All Users Profile%\DRM\WLM\TMAS_WLMHook.dll
  • %All Users Profile%\DRM\WLM\TMAS_WLMHook.dll.EMS
  • %All Users Profile%\DRM\WLM\TMAS_WLMMon.exe

Step 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_PLUGX.WLM 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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