BKDR_EMDIVI.YUR

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.

It gathers certain information on the affected computer.

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 drops and executes the following files:

• %User Temp%\vmater.exe -> detected as BKDR_EMDIVI.YUR
• %User Temp%\270529.docx -> decoy document

(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:

• 72af4f0cadebcad7d7443a2c72859c0a

Autostart Technique

This backdoor 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,%User Temp%\vmater.exe,"

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

• %User Startup%\vmater.lnk -> pointed to vmater.exe
• %Common Startup%\vmater.lnk -> pointed to vmater.exe

(Note: %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.. %Common Startup% is the system's shared Startup folder, which is usually C:\Documents and Settings\All Users\Start Menu\Programs\Startup on Windows 2000, XP, and Server 2003.)

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}eworld.jp/feeds.php
• http://www.{BLOCKED}norei.com/blog/index.php
• http://may.{BLOCKED}b.biz

As of this writing, the said sites are inaccessible.

Information Theft

This backdoor gathers the following information on the affected computer:

• Host name
• Process ID of the malware
• Internet Explorer Version
• OS Information (Major Version, Minor Version and Build Number)
• System Language
• Country/Region
• Time Zone Information

Other Details

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

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

NOTES:

It does not execute properly if the hostname is similar to the following strings:

• wilbert-SC1508
• xp-sp3-template
• mip-xp-cht
• CWS01_03
• wilbert-SC2202
• CWS05D102

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 any of the said strings, it pauses the execution of its malicious routine by performing a Sleep command.

It uses a Microsoft Word document icon then drops and opens a non-malicious file %User Temp%\270529.docx to deceive users that it is a normal file.

It does not have rootkit capabilities.

It does not exploit any vulnerability.