BKDR_EMOGEN.YHB

August 08, 2014
 Analysis by: Jaime Benigno Reyes
 ALIASES:

Mal/Emogen-Y (Sophos)

 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: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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

  TECHNICAL DETAILS

File Size:

36,352 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

04 Aug 2014

Payload:

Compromises system security, Collects system information, Terminates processes

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 non-malicious files:

  • %User Temp%\~numk217{random number}.tmp

(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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

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

  • Download end execute arbitrary files
  • Perform remote shell commands
  • Start and terminate processes and threads
  • Enumerate files
  • Get operating system configuration, security information, product ID, and hardware properties, such as RAM, disk space, and network cards
  • Delete NTLDR
  • Shut down the computer

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

  • {BLOCKED}.{BLOCKED}.87.26:443/b?P={generated value}
  • {BLOCKED}.{BLOCKED}.4.78:443/b?P={generated value}

As of this writing, the said sites are inaccessible.

Download Routine

This backdoor accesses the following websites to download files:

  • http://blogs.{BLOCKED}o.co.jp/sukuzi2012008/9695716.html
  • http://blogs.{BLOCKED}o.co.jp/komatsu20120809/37508778.html

It saves the files it downloads using the following names:

  • %User Temp%\index~k{random number}.htm - contains the address of the C&C server

(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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Information Theft

This backdoor gathers the following data:

  • Computer name
  • Drive type
  • Operating system and version
  • Language

  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

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

Identify and terminate files detected as BKDR_EMOGEN.YHB

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

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.  
  • %User Temp%\index~k{random number}.htm - contains the address of the C&C server
  • %User Temp%\~numk217{random number}.tmp

Step 5

Scan your computer with your Trend Micro product to delete files detected as BKDR_EMOGEN.YHB. 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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