Analysis by: Cris Nowell Pantanilla
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This backdoor arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

It does not have any propagation routine.

However, as of this writing, the said sites are inaccessible.

It does not have any downloading capability.

It does not have any information-stealing capability.

  TECHNICAL DETAILS

File Size: 40,960 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 08 Dec 2011
Payload: Connects to URLs/IPs

Arrival Details

This backdoor arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

Installation

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

  • DKK&^*#FD

It injects threads into the following normal process(es):

  • Explorer.exe

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\Local AppWizard-GeneraTed Applications\
bricks

HKEY_CURRENT_USER\Software\Local AppWizard-GeneraTed Applications\
bricks\Recent File List

HKEY_CURRENT_USER\Software\Local AppWizard-GeneraTed Applications\
bricks\Settings

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

This backdoor connects to the following URL(s) to send and receive commands from a remote malicious user:

  • {BLOCKED}n.dyndns-mail.com
  • {BLOCKED}mofa.dyndns-office.com

However, as of this writing, the said sites are inaccessible.

Download Routine

This backdoor does not have any downloading capability.

Information Theft

This backdoor does not have any information-stealing capability.

NOTES:

The malware gets the default Internet browser of the affected system by querying the following registry entry:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\http\shell\open\command
(default) = "{path and filename of Internet Browser}"

It then injects a thread in the browser if an instance of it is running. If the browser is found to be not running, the malware opens a new process of the said browser where it injects its thread that connects to the remote server. This enables the remote user to execute arbitrary commands on the affected system.

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 8.634.04
FIRST VSAPI PATTERN DATE: 09 Dec 2011
VSAPI OPR PATTERN File: 8.635.00
VSAPI OPR PATTERN Date: 10 Dec 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

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.

  • In HKEY_CURRENT_USER\Software\Local AppWizard-GeneraTed Applications\
    • bricks

Step 4

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