W2KM_BARTALEX.XTTD

August 06, 2015
 Analysis by: Jon Dexter Laurin
 ALIASES:

TrojanDownloader:O97M/Bartallex (Microsoft); W97M,Downloader (Symantec); Trojan-Downloader.MSWord.Agent.In (Kaspersky); VBA/TrojanDownloader.Agent.TH (ESET-NOD32); Troj/DocDI-PZ (Sophos); Trojan-Downloader.VBA.Agent (Ikarus)

 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

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.

It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system. As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

88,064 bytes

File Type:

DOC

Memory Resident:

No

Initial Samples Received Date:

04 Jun 2015

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 drops the following files:

  • %User Temp%\{random number}.bat
  • %User Temp%\{random number}.vbs
  • %User Temp%\{random number}.ps1 - for Windows Vista and above only

(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.)

Download Routine

This Trojan accesses the following websites to download files:

  • http://{BLOCKED}c.su/5607313.png
  • http://{BLOCKED}c.su/5605265.png

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

  • http://{BLOCKED}na-it-consulting.nl/wp-admin/images/pa.exe

It connects to the following URL(s) to download its configuration file:

  • http://{BLOCKED}engineservant.com/affiliates/fonts/67153178.txt
  • http://{BLOCKED}engineservant.com/affiliates/fonts/lns.txt
  • http://{BLOCKED}potson.com/wp-includes/certificates/67153178.txt
  • http://{BLOCKED}potson.com/wp-includes/certificates/lns.txt

It saves the files it downloads using the following names:

  • %User Temp%\8.exe - detected as TSPY_FAREIT.CERW
  • %User Temp%\444.jpg

(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.

As of this writing, the said sites are inaccessible.

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.710.09

FIRST VSAPI PATTERN DATE:

04 Jun 2015

VSAPI OPR PATTERN File:

11.711.00

VSAPI OPR PATTERN Date:

05 Jun 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_BARTALEX.XTTD. (Note: Please skip this step if the threats listed below have already been removed.)

    TSPY_FAREIT.CERW

Step 4

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 number}.bat
  • %User Temp%\{random number}.vbs
  • %User Temp%\{random number}.ps1
  • %User Temp%\444.jpg

Step 5

Scan your computer with your Trend Micro product to delete files detected as W2KM_BARTALEX.XTTD. 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.

Step 6

Enable the macro virus protection in Microsoft Office Applications

[ Learn More ]


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