Analysis by: Pearl Charlaine Espejo
ALIASES:

Win32/TrojanDownloader.Agent.BSW (ESET-NOD32); Trojan-Downloader.Win32.Agent (Ikarus); Trojan.DownLoader18.26290 (DrWeb)

 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: Dropped by other malware, Downloaded from the Internet

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 does not have any propagation routine.

It does not have any backdoor routine.

It accesses websites to download files. This action allows this malware to possibly add other malware on the affected computer. As of this writing, the said sites are inaccessible.

It deletes itself after execution. It gathers information and reports it to its servers.

  TECHNICAL DETAILS

File Size: 34,211,840 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 24 Dec 2015
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.

Installation

This Trojan drops and executes the following files:

  • %User Profile%\Applications\Microsoft\csviewer.exe - modified copy of itself, dropped when user is not administrator, detected as TROJ_DLOADE.SMEZ
  • %Program Files%\Windows NT\Accessories\Microsoft\csviewer.exe - modified copy of itself, dropped when user is administrator, detected as TROJ_DLOADE.SMEZ

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)

It creates the following folders:

  • %Program Files%\Windows NT\Accessories\Microsoft
  • %User Profile%\Applications\Microsoft

(Note: %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

Autostart Technique

This Trojan drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\Outlook Messeges.lnk ← shortcut to its modified drop copy

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Propagation

This Trojan does not have any propagation routine.

Backdoor Routine

This Trojan does not have any backdoor routine.

Download Routine

This Trojan accesses websites to download the following files:

  • http://info.{BLOCKED}hk.com/rss/video.php

It saves the files it downloads using the following names:

  • %User Temp%\msupdata.exe - it will be executed
  • %User Temp%\{random}.tmp – this will be created if unable to create 'msupdata.exe', it will be executed

(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.)

As of this writing, the said sites are inaccessible.

Other Details

This Trojan deletes itself after execution.

It gathers the following information and reports it to its servers:

  • OS Version

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 12.240.08
FIRST VSAPI PATTERN DATE: 29 Dec 2015
VSAPI OPR PATTERN File: 12.241.00
VSAPI OPR PATTERN Date: 30 Dec 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

Restart in Safe Mode

[ Learn More ]

Step 4

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %Program Files%\Windows NT\Accessories\Microsoft
  • %User Profile%\Applications\Microsoft

Step 5

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 Startup%\Outlook Messages.lnk
  • %User Temp%\msupdata.exe
  • %User Temp%\{random}.tmp

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DLOADE.SMEZ. 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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