Analysis by: Sammy Chua
ALIASES:

TrojanDownloader:W97M/Donoff (Microsoft); W97M.Downloader (Symantec); Trojan-Downloader.MSWord.Agent.ok (Kaspersky); W97M/Downloader.aka (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

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.

It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size: Varies
File Type: DOC
Memory Resident: No
Initial Samples Received Date: 09 Jul 2015

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.

Download Routine

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

  • http://{BLOCKED}net-marc-dugue.com/43/82.exe
  • http://{BLOCKED}asynth.com/43/82.exe

It saves the files it downloads using the following names:

  • %User Temp%\rebuil3.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.)

Trend Micro detects the dowloaded file as:

  • TSPY_DRIDEX.WJW

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

  SOLUTION

Minimum Scan Engine: 9.750
FIRST VSAPI PATTERN FILE: 11.780.05
FIRST VSAPI PATTERN DATE: 09 Jul 2015
VSAPI OPR PATTERN File: 11.781.00
VSAPI OPR PATTERN Date: 10 Jul 2015

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

Remove malware/grayware files dropped/downloaded by W2KM_DLOADER.WJW. (Note: Please skip this step if the threats listed below have already been removed.)

     TSPY_DRIDEX.WJW

Step 4

Enable the macro virus protection in Microsoft Office Applications

[ Learn More ]

Step 5

Scan your computer with your Trend Micro product to delete files detected as W2KM_DLOADER.WJW. 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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