Analysis by: Christopher Daniel So
ALIASES:

TrojanDownloader:Win32/Dalexis (Microsoft), Win32/TrojanDownloader.Elenoocka.C (ESET), W32/Elenoocka.C!tr.dldr (Fortinet)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • 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.

  TECHNICAL DETAILS

File Size: 73,728 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 12 May 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%\{malware file name}.rtf - a non malicious decoy file
  • %User Temp%\{random file name}.cab - contains the RTF file

(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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • akixetbd

Download Routine

This Trojan accesses the following websites to download files:

  • http://{BLOCKED}ffair.org.au/wp-content/efax.jpg
  • http://{BLOCKED}c.{BLOCKED}ista.org/listini/efax.jpg
  • http://{BLOCKED}pineswebservices.com/testing/efax.jpg
  • http://{BLOCKED}ochef.com/wp-content/efax.jpg
  • http://{BLOCKED}enwijhe92.nl/diversen/efax.jpg
  • http://{BLOCKED}tric.hostei.com/pub/efax.jpg
  • http://{BLOCKED}all.com/logs/efax.jpg
  • http://{BLOCKED}ep.nl/images/efax.jpg
  • http://{BLOCKED}x.de/system/efax.jpg
  • http://{BLOCKED}andstares.co.uk/docs/efax.jpg
  • http://www.{BLOCKED}te4u.eu/aglextra/efax.jpg

It saves the files it downloads using the following names:

  • %User Temp%\{random file name}.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:

  • TROJ_CRYPCTB.YVU

Other Details

This Trojan opens the following files:

  • %User Temp%\{malware file name}.rtf

(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.)

  SOLUTION

Minimum Scan Engine: 9.750
VSAPI OPR PATTERN File: 11.607.00
VSAPI OPR PATTERN Date: 16 Apr 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

Remove the malware/grayware file dropped/downloaded by TROJ_DALEXIS.YVM. (Note: Please skip this step if the threat(s) listed below have already been removed.)

  • TROJ_CRYPCTB.YVU

Step 3

Identify and terminate files detected as TROJ_DALEXIS.YVM

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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%\{malware file name}.rtf
  • %User Temp%\{random file name}.cab

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_DALEXIS.YVM. 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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