Analysis by: RonJay Kristoffer Caragay
ALIASES:

VirTool:Win32/DelfInject (Microsoft); Trojan-Dropper.Win32.Dapato.orgn (Kaspersky);

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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 uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 503,808 bytes
File Type: EXE
Initial Samples Received Date: 17 Jan 2017

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:

  • %System%\Tasks\Microsoft\Windows\Windows Media Sharing\MediaCheckUpdate
  • %System%\Tasks\Microsoft\Windows\Windows Media Sharing\MediaIdle
  • %System%\Tasks\Microsoft\Windows\Windows Media Sharing\WinMediaShare

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It drops the following copies of itself into the affected system:

  • %Application Data%\Microsoft\Windows\winmedia9.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 uses Windows Task Scheduler to create a scheduled task that executes the dropped copy.

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
WinMediaShare = "%Application Data%\Microsoft\Windows\winmedia9.exe"

Dropping Routine

This Trojan drops the following files:

  • %Application Data%\{random}.exe
  • %Application Data%\todo.cmd
  • %Application Data%\upx.exe
  • %Application Data%\au3cds.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.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://i.{}BLOCKED}r.com/{random}.png
  • https://{BLOCKED}yip.com/xml
  • https://i.{BLOCKED}e.org/{random}.png
  • https://{BLOCKED}ig.co/json
  • https://{BLOCKED}og1.blogspot.com.br/
  • http://{BLOCKED}3.ax.lt/au3meta.png
  • http://{BLOCKED}3.ax.lt/download.php
  • http://{BLOCKED}3.ax.lt/i.php?e={value}
  • http://{BLOCKED}3.ax.lt/i.php?l={value}
  • http://{BLOCKED}3.ax.lt/pedll2.png
  • http://www.{BLOCKED}um.com.br/wp-content/themes/kingsize/m2.exe
  • http://www.{BLOCKED}um.com.br/wp-content/themes/kingsize/rs6.exe

It deletes the initially executed copy of itself