W2KM_DLOAD.XTUW

February 21, 2017
 Analysis by: Pearl Charlaine Espejo
 ALIASES:

W97M/Downldr.gen (Cyren); W97M/Downloader.bvc (McAfee); W97M.Downloader (Symantec); Troj/DocDl-HFP (Sophos); W97M/Downldr.gen (F-Prot)

 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:

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

This Trojan 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.

  TECHNICAL DETAILS

File Size:

236,032 bytes

File Type:

DOC

Memory Resident:

No

Initial Samples Received Date:

08 Feb 2017

Payload:

Connects to URLs/IPs, Downloads files

Arrival Details

This Trojan 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 adds the following processes:

  • eventvwr.exe -> Event Viewer

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CURRENT_USER\Software\Classes\
mscfile\shell\open\
command
(Default) = "%User Temp%\ui788.exe"

Note: This method is set by the malware to make downloaded file the default program/application in opening .msc files

Download Routine

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

  • https://a.{BLOCKED}aps.me/ui788.exe

It saves the files it downloads using the following names:

  • %User Temp%\ui788.exe

(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.)

As of this writing, the said sites are inaccessible.

Other Details

This Trojan does the following:

  • It executes its commands using Windows powershell.
  • It executes the command PING -n 15 127.0.0.1>nul to perform a Sleep for 15 seconds before running the downloaded file.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.208.02

FIRST VSAPI PATTERN DATE:

08 Feb 2017

VSAPI OPR PATTERN File:

13.209.00

VSAPI OPR PATTERN Date:

09 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

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\Classes\mscfile\shell\open\command
    • (Default) = "%User Temp%\ui788.exe"

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%\ui788.exe

Step 5

Scan your computer with your Trend Micro product to delete files detected as W2KM_DLOAD.XTUW. 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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