BKDR_SIMBOT.TRWR

 Analysis by: Anthony Joe Melgarejo

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet

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 executes commands from a remote malicious user, effectively compromising the affected system.

It terminates itself if it detects it is being run in a virtual environment.

  TECHNICAL DETAILS

File Size:

144,896 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

20 Oct 2014

Payload:

Compromises system security, Steals information

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:

  • %Windows%\msplugin.ps

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

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

  • 78@WMIRCOM

It injects codes into the following process(es):

  • svchost.exe

Autostart Technique

This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Device Enumerator Service
Type = "10"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Device Enumerator Service
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Device Enumerator Service
ErrorControl = "1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Device Enumerator Service
ImagePath = "{malware path and file name} -k"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Device Enumerator Service
DisplayName = "Device Enumerator Service"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Device Enumerator Service
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Device Enumerator Service
Description = "Enables applications to transfer and synchronize content using removable mass-storage devices."

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Device Enumerator Service

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Device Enumerator Service\Security

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Device Enumerator Service\Enum

It adds the following registry entries:

HKEY_LOCAL_MACHINE\Software\AppDataLow\
Software\Microsoft\svchost
BinData = "{encrypted C&Cs}"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Download and execute arbitrary files - saved as %User Temp%\svc{random number}.tmp or %User Temp%\sae{random number}.tmp

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

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

  • http://{BLOCKED}ds.de/cart/adm/in.php
  • http://www.{BLOCKED}ng.de/a_inc/bbs/read_comment_update.php
  • http://www.{BLOCKED}c.org/intraweb/mantisbt/admin/install_db.php
  • http://www.{BLOCKED}e.ac.jp/modalfiles/opinion.php
  • http://www.{BLOCKED}g.de/backup/includes/domit/don_xmlrpc_client.php
  • http://www.{BLOCKED}neksda.com.au/modules/board/conf/module.php

As of this writing, the said servers are currently inaccessible.

Information Theft

This backdoor gathers the following data:

  • Network Adapter information
  • Operating System version
  • System time
  • Computer name

Other Details

This backdoor terminates itself if it detects it is being run in a virtual environment.

NOTES:

It checks if it is running under the following virtual environment:

  • VMWare
  • VirtualBox

  SOLUTION

Minimum Scan Engine:

9.700

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.

  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • Device Enumerator Service

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_LOCAL_MACHINE\Software\AppDataLow\Software\Microsoft\svchost
    • BinData = "{encrypted C&Cs}"

Step 5

Search and delete this file

[ 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.
  • %Windows%\msplugin.ps
  • %User Temp%\svc{random number}.tmp
  • %User Temp%\sae{random number}.tmp

Step 6

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

Step 7

Scan your computer with your Trend Micro product to delete files detected as BKDR_SIMBOT.TRWR. 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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