Analysis by: Kathleen Notario

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It does not have any propagation routine.

It connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size: 665,600 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 03 Oct 2011

Arrival Details

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This backdoor drops the following files:

  • %User Temp%\~TX{number}.TMP - also detected as BKDR_DARKMOON.SM1

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)

It drops the following non-malicious file:

  • %Current%\{malware filename}.pdf

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • *^%fahk)F

It stays memory-resident by injecting codes into the following processes:

  • explorer.exe

Other System Modifications

This backdoor adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{6B808548-D083-A635-C7BB-B37E45A98DE7}
StubPath = "C:\Windows\system32:ctfmonn.exe"

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

HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\
\Settings

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{6B808548-D083-A635-C7BB-B37E45A98DE7}

HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\
\Recent File List

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

This backdoor connects to the following websites to send and receive information:

  • http://{BLOCKED}dns.{BLOCKED}ns-blog.com
  • 1j.{BLOCKED}w1.biz

NOTES:

It queries the default web browser by accessing the following registry entry:

HKEY_CLASSES_ROOT\http\shell\open\command

It then launches a hidden Web browser process (e.g. iexplore.exe) where this malware injects its code for its backdoor routines.

This backdoor has the following capabilities:

  • Capture screen shots, webcam, audio
  • Delete, search, and upload files
  • Download and inject remote codes to legitimate processes
  • Log keystrokes and active window
  • Manage processes and services
  • Modify and search the registry entries
  • Perform a shell command
  • Send system information (IP address, computer name, user name, operating system)
  • Update/Uninstall the malware
  • View and terminate active windows and ports

This backdoor does not have rootkit capabilities.

This backdoor does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.470.12
FIRST VSAPI PATTERN DATE: 03 Oct 2011
VSAPI OPR PATTERN File: 8.471.00
VSAPI OPR PATTERN Date: 04 Oct 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 BKDR_DARKMOON.SM1

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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_CURRENT_USER\Software\Local AppWizard-Generated Applications
    • Settings
  • In HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications
    • Recent File List
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {6B808548-D083-A635-C7BB-B37E45A98DE7}

Step 5

Search and delete this file

[ Learn More ]
There may be some component 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.  
  • %Current%\{malware filename}.pdf

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_DARKMOON.SM1. 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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