TROJ_DOWEXEF.A

April 28, 2016
 Analysis by: Rhena Inocencio
 ALIASES:

TrojanDownloader:Win32/Dowexef.B (Microsoft), a variant of Win32/TrojanDownloader.Agent.BRC trojan (ESET), Trojan.Phytob (Symantec)

 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

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

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

  TECHNICAL DETAILS

File Size:

102,912 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

25 Apr 2016

Payload:

Connects to URLs/IPs, Displays message/message boxes

Arrival Details

This Trojan may be downloaded from the following remote site(s):

  • http://{BLOCKED}besplatno.pw/media/books/ebook.pdf.exe

Download Routine

This Trojan accesses the following websites to download files:

  • http://{BLOCKED}.{BLOCKED}.167.105/ajax-loader.gif

It saves the files it downloads using the following names:

  • %User Temp%\mcshield.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.)

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

Other Details

This Trojan does the following:

  • It displays a message box containing a fake error message:
    {TROJ_DOWEXEF.png}
  • It uses powershell to download and execute the file

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

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.490.01

FIRST VSAPI PATTERN DATE:

25 Apr 2016

VSAPI OPR PATTERN File:

12.491.00

VSAPI OPR PATTERN Date:

26 Apr 2016

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

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%\mcshield.exe

Step 4

Scan your computer with your Trend Micro product to delete files detected as TROJ_DOWEXEF.A. 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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