Analysis by: John Kevin Sanchez
ALIASES:

W32/Kryptik.FLXL!tr (Fortinet), Trojan:Win32/Dynamer!ac (Microsoft)

 PLATFORM:

Windows

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

  • Threat Type: Spyware

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet, Dropped by other malware

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

As of this writing, the said sites are inaccessible.

It connects to certain websites to send and receive information. It deletes itself after execution.

  TECHNICAL DETAILS

File Size: 491,520 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 03 Feb 2017
Payload: Connects to URLs/IPs, Steals information, Downloads files

Arrival Details

This spyware 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 spyware drops the following files:

  • %User Temp%\Tar{random digits}.tmp - contains system information

(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 injects codes into the following process(es):

  • explorer.exe

Other System Modifications

This spyware adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
EventSubsystem

Download Routine

This spyware accesses the following websites to download files:

  • http://{BLOCKED}enpost.org/uploads/ad5413d5da03f42231b3892fdfcf4084.png
  • http://{BLOCKED}.{BLOCKED}.22.206/safari/confirm?ocr=552927891723
  • http://{BLOCKED}.{BLOCKED}.77.109/timetable/ballet?bigleti=42007347811

As of this writing, the said sites are inaccessible.

Information Theft

This spyware gathers the following data:

  • OS Version
  • Computer Name
  • User Name
  • Running process

Other Details

This spyware connects to the following website to send and receive information:

  • http://{BLOCKED}c.co.kr/report_N_0053_{hex value}_{step number}_{report status}
  • http://{BLOCKED}c.co.kr/report_N_0053_{hex value}_0_started_ext_ALRRR_{value}_OSBBB_{OS architecture}_OSNNN_{OS}_CNNN_{Computer Name}_UNNN_{UserName}_EXXX_

It deletes itself after execution.

NOTES:

This spyware executes the following command:

  • CMD /C SYSTEMINFO & SYSTEMINFO & SYSTEMINFO & SYSTEMINFO &SYSTEMINFO & DEL {original malware copy}

Where {report status} can be any of the following:

  • already_active
  • already_ok
  • crc_ok
  • except
  • except_detail_
  • executed_ok
  • finished
  • gdiplus_not_ok
  • gdiplus_ok
  • image_not_ok
  • image_ok
  • image_size_not_ok
  • image_size_ok
  • image_type_not_ok
  • image_type_ok
  • mark_already
  • mark_not_setted
  • mark_ok
  • mark_setted
  • page_err
  • page_ok
  • payload_executed
  • payload_file_delete_ok
  • payload_file_name_ok
  • payload_file_run_ok
  • payload_file_wait_ok
  • payload_file_write_ok
  • payload_mem_not_ok
  • payload_mem_ok
  • payload_not_ok
  • payload_ok
  • payload_size_ok
  • payload_type_bad
  • payload_type_exe
  • payload_type_exe_wait_del
  • payload_type_shell
  • process_{running process}
  • started_ext_
  • step_0
  • step_1
  • step_2
  • step_3
  • step_4
  • watch2_err_{digits}
  • watch2_start_{digits}_{digits}
  • watch2_finish_{digits}_{digits}__{digits}
  • http__{BLOCKED}enpost.org/uploads/ad5413d5da03f42231b3892fdfcf4084.png

This malware relies on steganography to evade detection. It connects to specific URLs to download a stock image, where majority of its routines are embedded. It then extracts the following from the downloaded image:

  • Arbitrary code
  • List of URLs to be accessed

The malware avoids to execute its malicious behavior if the computer name is MIKE-PC.

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 13.220.08
FIRST VSAPI PATTERN DATE: 14 Feb 2017
VSAPI OPR PATTERN File: 13.221.00
VSAPI OPR PATTERN Date: 15 Feb 2017

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 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\Microsoft
    • EventSubsystem

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.
  • %User Temp%\~{random digits}.tmp

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TSPY_GATAK.SM4. 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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