Backdoor.Win32.REMCOS.UNGB

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

However, as of this writing, the said sites are inaccessible. It gathers information and reports it to its servers.

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 folders:

• %AppDataLocal%\Lsz
• %Application Data%\oreo

(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It drops the following files:

• %AppDataLocal%\Lsz\Lsz
• %AppDataLocal%\Lsz\Lsznxy.exe
• %AppDataLocal%\Lsz\Lszsex.vbs {executes Lsznxy.exe}
• %Application Data%\oreo\logs.dat
• %System Root%\Users\{user name}\Contacts\Nex
• %User Temp%\Lsz
• %User Temp%\Lszeql.exe

(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Roaming on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It drops and executes the following files:

• %User Temp%\Jndrs.js {executes Lszeql.exe} - deleted after execution

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

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

• Remcos_Mutex_Inj

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Lsz = %AppDataLocal%\Lsz\Lszsex.vbs

Other System Modifications

This Backdoor adds the following registry entries:

HKEY_CURRENT_USER\Software\{random}
EXEpath = {hex values}

Backdoor Routine

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

• Acquire user passwords and login data
• Activate keylogger
• Capture audio
• Capture image
• Capture screen
• Check upload progress
• Clear clipboard data
• Clear cookies and stored browser logins
• Copy clipboard data
• Create new directory
• Delete file/s
• Delete keylogs
• Display messagebox
• Download file from local
• Download file from URL
• Enumerate process
• Execute command/s
• List all drives
• List all files
• Manipulate a window
• Manipulate registry entries
• Open webpage
• Perform ping
• Rename file/s
• Run the Command Prompt (CMD)
• Search file/s
• Send keyboard input
• Send mouse click
• Set clipboard data
• Terminate process
• Uninstall itself
• Update itself
• Upload file/s

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

• {BLOCKED}.{BLOCKED}.202.61:52019

Other Details

However, as of this writing, the said sites are inaccessible.

It gathers the following information and reports it to its servers:

• Computer Name
• Operating System Version
• Product Name
• Primary Adapter
• User Access (Admin or Non-admin)
• User Profile
• User Name
• User Domain
• Processor Revision No.
• Processor Level
• Processor Identifier
• Processor Architecture
• System Type (32-bit or 64-bit)