TROJ_DOWNEKS.B

 Analysis by: John Anthony Banes

 ALIASES:

Trojan-Downloader.Win32.Downeks.c (Kaspersky); Trojan.Downeks (NORTON); Troj/DwnLdr-RLP (Sophos_Lite)

 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:

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

It steals certain information from the system and/or the user.

It connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size:

1,838,080 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

06 Feb 2017

Payload:

Steals information, Connects to URLs/IPs

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:

  • %Application Data%\{random numbers}

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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 drops and executes the following files:

  • %User Temp%\Readme.exe
  • %User Temp%\fasad.doc

(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:

  • qrr5flTFdYVLNlAuK5Xvmuynxf1a9rMY

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

Software\Microsoft\Windows\
CurrentVersion\Run
Download Excute = %Application Data%\Download Excute.exe

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

  • Readme.lnk

Download Routine

This Trojan saves the files it downloads using the following names:

  • %Application Data%\Download Excute.exe

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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.

Information Theft

This Trojan steals the following information:

  • Computer Name
  • User Name
  • Volume Serial Number of Drive C:
  • Operating System version
  • Installed .NET Framework versions
  • Processor Type
  • Screenshots
  • Security products installed on Program Files

Other Details

This Trojan connects to the following URL(s) to get the affected system's IP address:

  • http://myexternalip.com/raw

It connects to the following website to send and receive information:

  • dl.{BLOCKED}se.com

It does the following:

  • It checks if the following strings match the username:
    • abc
    • Admin or admin
    • antonie
    • antonis
    • Antony
    • Babbage
    • BUF
    • David
    • GT
    • John
    • Johnson
    • Klone
    • laptop1
    • luser
    • Miller
    • mini
    • Owner
    • PetMay
    • Public
    • Rivest
    • support
    • susan
    • swt_000
    • SYSTEM
    • test
    • User or user
    • Wilbert
    • worker
  • It checks for the existence of directories in Program Files with the following strings:
    • avira
    • avast
    • avg
    • eset
    • kaspersky
    • alwil
    • onecare
    • security
    • mcafee
    • symantec
    • norton
    • defender
    • bitdefender
  • It displays a message box with a message as defined by the server.

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.198.06

FIRST VSAPI PATTERN DATE:

03 Feb 2017

VSAPI OPR PATTERN File:

13.199.00

VSAPI OPR PATTERN Date:

04 Feb 2017

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

Delete this registry value

[ 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Download Excute = %Application Data%\Download Excute.exe

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.
  • %Application Data%\{random numbers}
  • %Application Data%\Download Excute.exe
  • %User Temp%\Readme.exe
  • %User Temp%\fasad.doc
  • %Startup%\Readme.lnk

Step 6

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