Backdoor.Win32.REMCOS.USMANEAGFO

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.

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:

• %Application Data%\remcos\

(Note: %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 copies of itself into the affected system:

• %AppDataLocal%\Uyxl\Uyxltrn.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).)

It drops the following files:

• %Desktop%\{malware filename minus last 7 characters} -> jpg file
• %AppDataLocal%\Uyxl\Uyxl -> copy of jpg file dropped in %Desktop%
• %AppDataLocal%\Uyxl\Uyxlmes.vbs -> script to run executable malware copy
• %AppDataLocal%\Uyxl\Uyxl_steo.hta -> script to run vbs file
• %User Temp%\uninstall.vbs -> uninstalls the malware
• %User Temp%\update.vbs -> updates the malware
• %User Temp%\restart.vbs -> restarts the malware
• %Application Data%\remcos\logs.dat -> record of user keystrokes
• %User Temp%\install.vbs -> installs the malware
• %Application Data%\remcos\remcos.exe

(Note: %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).. %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).. %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).. %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 adds the following mutexes to ensure that only one of its copies runs at any one time:

• Uyxl
• Remcos_Mutex_Inj
• Remcos-JTF5PJ
• Mutex_RemWatchdog

It injects codes into the following process(es):

• %System%\TapiUnattend.exe
• %System%\svchost.exe

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

It modifies file attributes to make files hidden.

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
Uyxl = %AppDataLocal%\Uyxl\Uyxl_steo.hta

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Policies\Run
remcos = %Application Data%\remcos\remcos.exe

Other System Modifications

This Backdoor adds the following registry entries:

HKEY_CURRENT_USER\Software\Remcos-JTF5PJ
exepath = {hex values}

HKEY_CURRENT_USER\Software\Remcos-JTF5PJ
licence = {random}

HKEY_CURRENT_USER\Software\Remcos-JTF5PJ
WD = 3492

HKEY_CURRENT_USER\Software\Remcos-JTF5PJ
pth_unenc = %System%\TapiUnattend.exe

HKEY_CURRENT_USER\Software\Remcos-JTF5PJ
v = 2.5.0 Pro

Backdoor Routine

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

• sdfklxcjv8r89234uijxdzsfsrfwdfsdf.{BLOCKED}c.net

Information Theft

This Backdoor gathers the following data:

• Computer name
• User name
• Home drive
• Logon server
• Processor architecture
• Windows version
• System type (x64, x86)
• User access (if admin or not)
• Memory information
• Browser logins and cookies
• User keystrokes
• Session name
• User profile
• User domain

Other Details

Based on analysis of the codes, it has the following capabilities:

• Delete files
• Rename files
• Upload files
• Download files
• Browse directories
• Obtain file/directory attributes
• Execute files
• Open files
• Activate keylogger
• Copy and paste text to and from clipboard
• Create shortcuts
• Retrieve logins and cookies from the following browsers:
  • Google Chrome
  • Mozilla Firefox
  • Internet Explorer
• Ping an address
• Display a messagebox
• Shutdown machine
• Put machine to sleep
• Terminate processes
• Perform registry changes
• Display image
• Play alarm
• Play/record audio
• List windows
• Send keyboard/mouse input
• Execute shell commands
• Open the command prompt
• Open the event viewer
• Use the camera