BKDR_SIMBOT.YJK

 Analysis by: Rhena Inocencio
 Modified by: Janus Agcaoili

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • 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 executes then deletes itself afterward.

  TECHNICAL DETAILS

File Size:

71,680 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

14 Apr 2016

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:

  • %Program Files%\Ram.exe <- deleted afterwards
  • %Program Files%\setting32.ini <- deleted afterwards

(Note: %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)

It drops and executes the following files:

  • %Program Files%\mshelp32.exe <- deleted afterwards
  • %Program Files%\vxvarsx32.bat <- deleted afterwards
  • %Program Files%\各学科代表.xls
  • %Application Data%\MMC\MMC.exe

(Note: %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.. %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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 executes then deletes itself afterward.

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\software\microsoft\
windows\currentversion\run
msnetbridge = "%Application Data%\MMC\MMC.EXE"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}time.info/index.php

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.466.03

FIRST VSAPI PATTERN DATE:

14 Apr 2016

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Restart in Safe Mode

[ Learn More ]

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\currentversion\run
    • msnetbridge = "%Application Data%\MMC\MMC.EXE"

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.
  • %Program Files%\Ram.exe
  • %Program Files%\setting32.ini
  • %Program Files%\mshelp32.exe
  • %Program Files%\vxvarsx32.bat
  • %Program Files%\各学科代表.xls
  • %Application Data%\MMC\MMC.exe

Step 6

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