BKDR_EMDIVI.ZJCG-C

This backdoor arrives as an attachment to email messages spammed by other malware/grayware or malicious users. It 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 as an attachment to email messages spammed by other malware/grayware or malicious users.

It 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%\vmpress.exe - detected as BKDR_EMDIVI.ZJCG-C
• %User Temp%\jsme20150728.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:

• fe331ca6c0f441e3465e356028cfeffc

Autostart Technique

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

• %Common Startup%\vmpress.lnk - shortcut pointing to vmpress.exe

(Note: %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, and C:\ProgramData\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

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}a.com/snow/index.php
• http://jp.{BLOCKED}b.biz/{random 5 numbers}?p=#

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
• Memory Size (RAM)

Other Details

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

• http://www.microsoft.com/en-us/default.aspx
• http://www.msftncsi.com/ncsi.txt
• http://www.yahoo.co.jp

NOTES:

It does not execute properly if the host name is similar to any of 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 Word document icon, then drops and opens a non-malicious file %User Temp%\jsme20150728.docx to deceive users that it is a normal file.