Analysis by: Jimelle Monteser
 Modified by: Nikko Tamana
ALIASES:

Troj/DwnLdr-LEP (Sophos)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • 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.

  TECHNICAL DETAILS

File Size: 110,592 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 28 Nov 2013
Payload: 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.

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CLASSES_ROOT\Cad.Document

HKEY_CLASSES_ROOT\Cad.Document\DefaultIcon

HKEY_CLASSES_ROOT\Cad.Document\shell

HKEY_CLASSES_ROOT\Cad.Document\shell\
open

HKEY_CLASSES_ROOT\Cad.Document\shell\
open\command

HKEY_CLASSES_ROOT\Cad.Document\shell\
print

HKEY_CLASSES_ROOT\Cad.Document\shell\
print\command

HKEY_CLASSES_ROOT\Cad.Document\shell\
printto

HKEY_CLASSES_ROOT\Cad.Document\shell\
printto\command

It adds the following registry entries:

HKEY_CLASSES_ROOT\Cad.Document
Default = "Cad Document"

HKEY_CLASSES_ROOT\Cad.Document
Default = "{malware path}\{malware filename}.exe,0"

HKEY_CLASSES_ROOT\Cad.Document\shell\
open\command
Default = "{malware path}\{malware filename}.exe "%1""

HKEY_CLASSES_ROOT\Cad.Document\shell\
print\command
Default = "{malware path}\{malware filename}.exe /p "%1""

HKEY_CLASSES_ROOT\Cad.Document\shell\
printto\command
Default = "{malware path}\{malware filename}.exe /pt "%1" "%2" "%3" "%4""

Download Routine

This Trojan downloads the file from the following URL and renames the file when stored in the affected system:

  • http://{BLOCKED}n-foundation.ro/images/tere.exe
  • http://{BLOCKED}ri-gagyi.com/images/tere.exe
  • http://{BLOCKED}ni.net/wp-content/uploads/tere.exe
  • http://{BLOCKED}tbot.com/bots/tere.exe
  • http://{BLOCKED}i.org/wp-content/uploads/2012/02/tere.exe

It saves the files it downloads using the following names:

  • %User Temp%\{random file name}.exe - Detected as TSPY_ZBOT.BWJ
  • %Temporary Internet Files%\Content.IE5\{random folder name}\tere[1].exe - Detected as TSPY_ZBOT.BWJ

(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 and 7.. %Temporary Internet Files% is the Temporary Internet Files folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temporary Internet Files on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Microsoft\Windows\Temporary Internet Files on Windows Vista and 7.)

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

NOTES:

TROJ_DLOADR.BWJ is executed every time a CAD document is executed or printed.

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 10.440.03
FIRST VSAPI PATTERN DATE: 28 Nov 2013
VSAPI OPR PATTERN File: 10.441.00
VSAPI OPR PATTERN Date: 29 Nov 2013

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

Remove malware/grayware files dropped/downloaded by TROJ_DLOADR.BWJ

    • TSPY_ZBOT.BWJ

Step 3

Scan your computer with your Trend Micro product and note files detected as TROJ_DLOADR.BWJ

Step 4

Delete this registry key

[ 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_CLASSES_ROOT
    • Cad.Document

Step 5

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%\{random file name}.exe
  • %Temporary Internet Files%\Content.IE5\{random folder name}\tere[1].exe

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_DLOADR.BWJ. 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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