BKDR_EMDIVI.F

 Analysis by: Adrian Cofreros

 ALIASES:

HEUR:Trojan.Win32.Generic(Kaspersky),a variant of Win32/Agent.WGN(NOD32)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware


This backdoor 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 executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size:

203,776 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

01 Oct 2014

Payload:

Executes files

Arrival Details

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

  • 9419a911dd211fba4fd81dd417ef3f47

Autostart Technique

This backdoor drops the following shortcut pointing to its copy in the User Startup folder to enable its automatic execution at every system startup:

  • %ProgramData%\Microsoft\Windows\Start Menu\Programs\Startup\FlashUtil_ActiveX.lnk-lnk to the malware(Windows 7 and Vista)
  • %User Startup%\FlashUtil_ActiveX.lnk-lnk to the malware(Windows XP)
  • %Application Data%\Microsoft\Windows\Start Menu\Programs\Startup\FlashUtil_ActiveX.lnk-lnk to the malware(Windows 7 and Vista)
  • %All Users Profile%\Start Menu\Programs\Startup\FlashUtil_ActiveX.lnk-lnk to the malware(Windows XP)

(Note: %ProgramData% is the Program Data folder, where it usually is C:\Program Files in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData in 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.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.. %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.. %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData 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 modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = "%System%\userinit.exe,{malware path}\{malware filename},"

(Note: The default value data of the said registry entry is %System%\userinit.exe,.)

Propagation

This backdoor does not have any propagation routine.

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Enumerate files and folders
  • Delete files and folders
  • Download files
  • Upload files
  • Execute files
  • Get file attributes
  • Enumerate processes
  • Perform remote shell
  • Loads a library using LoadLibrary API
  • Import functions from a library using GetProcAddress API
  • Gather credentials using CredEnumerate or PStoreCreateInstance API
  • Gather Firefox settings from prefs.js
  • Gather proxy settings from proxy.pac
  • Gather proxy settings from windows registry
  • Sleep

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://www.{BLOCKED}.{BLOCKED}a.gr.jp/info/yougo/book/index.php
  • http://www.{BLOCKED}c.{BLOCKED}o.jp/view6/viewdata/book/index.php

Other Details

This backdoor connects to the following URL(s) to check for an Internet connection:

  • http://www.yahoo.co.jp
  • http://www.msftncsi.com
  • http://www.microsoft.com

NOTES:

It enumerates all visible windows and compares each window's title bar text with the following strings:

  • Ollydbg
  • W32Dasm
  • WireShark
  • SoftICE
  • Process Explorer
  • Process Monitor
  • Process Hacker

If a window's title bar text contains the said strings, it will pause the execution of its malicious routine by performing a Sleep command.

It does not have rootkit capabilities.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

11.182.03

FIRST VSAPI PATTERN DATE:

30 Sep 2014

VSAPI OPR PATTERN File:

11.183.00

VSAPI OPR PATTERN Date:

01 Oct 2014

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

Identify and delete files detected as BKDR_EMDIVI.F using either the Startup Disk or Recovery Console

[ Learn More ]

Step 4

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Userinit = "%System%\userinit.exe,{malware path}\{malware filename},"
      To: Userinit = %System%\userinit.exe,

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.
  • %ProgramData%\Microsoft\Windows\Start Menu\Programs\Startup\FlashUtil_ActiveX.lnk-lnk to the malware(Windows 7 and Vista)
  • %User Startup%\FlashUtil_ActiveX.lnk-lnk to the malware(Windows XP)
  • %Application Data%\Microsoft\Windows\Start Menu\Programs\Startup\FlashUtil_ActiveX.lnk-lnk to the malware(Windows 7 and Vista)
  • %All Users Profile%\Start Menu\Programs\Startup\FlashUtil_ActiveX.lnk-lnk to the malware(Windows XP)

Step 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_EMDIVI.F. 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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