Backdoor.MSIL.REMCOS.AOJ

 Modified by: Warren Adam Sto. Tomas

 ALIASES:

TR/AD.Remcos.caakn(AntiVir);

 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, Downloaded from the Internet, Spammed via email

This malware was seen delivered via malicious spam spoofing the brand DHL as the sender. It came as an .ISO attachment. It possibly is used for spearphishing activities.

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

  TECHNICAL DETAILS

File Size:

506,880 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

02 Nov 2019

Payload:

Connects to URLs/IPs

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 the following copies of itself into the affected system:

  • %User Profile%\OEM\systeminfo.exe

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

It drops the following files:

  • %Application Data%\remcos\logs.dat -> record of user's activities/keylogs

(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 adds the following processes:

  • {malware path and file name}
  • %Program Files%\Internet Explorer\iexplore.exe

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000(32-bit), Server 2003(32-bit), XP, Vista(64-bit), 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit) , or C:\Program Files (x86) in Windows XP(64-bit), Vista(64-bit), 7(64-bit), 8(64-bit), 8.1(64-bit), 2008(64-bit), 2012(64-bit) and 10(64-bit).)

It creates the following folders:

  • %Application Data%\remcos
  • %User Profile%\OEM

(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).. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name} 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
  • Remcos-{random}

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Windows
Load = "%User Profile%\OEM\systeminfo.exe"

Other System Modifications

This Backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\Remcos-{random}

It adds the following registry entries:

HKEY_CURRENT_USER\Software\remcos_{Random}
exepath = {hex values}

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

HKEY_CURRENT_USER\Software\Remcos-{random}
Inj = 1

Backdoor Routine

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

  • Activate keylogger
  • Capture audio, or stop capture
  • Capture screen
  • Change desktop wallpaper
  • Change, pause, stop, or start a service
  • Clear browser hisotry
  • Close a window
  • Close affected system's camera
  • Close connection
  • Connect to a specified server
  • Control affected system's camera
  • Deactive keylogger
  • Delete registry key/entry
  • Enumerate registry key/entry
  • Modify/add registry entry
  • Delete file or directory
  • Download a file
  • Read a file
  • Save a file
  • Upload a file
  • Empty clipboard data
  • Execute a command
  • Get active program's window title
  • Get clipboard data
  • Get process ID of a window
  • Get system information
  • Hide or show a window
  • List files in specified directory
  • List installed applications
  • List keyboard information
  • List running processes
  • List windows
  • Log off, restart, or shut down the affected system
  • Modify a window
  • Play an audio in the affected system
  • Restart itself
  • Show message box
  • Terminate a process
  • Terminate itself
  • Uninstall itself
  • Update itself

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

  • rennelautos.{BLOCKED}w.com:2404
  • rennelautos.{BLOCKED}o.org:2404
  • kellyben.{BLOCKED}o.org:2404
  • jkharding2014.{BLOCKED}s.net:2404
  • sunwap878.{BLOCKED}s.net:2404
  • sunwap878.{BLOCKED}u.net:2404
  • jessen.{BLOCKED}o.org:2404
  • jessen.{BLOCKED}s.rocks:2404

Other Details

This Backdoor does the following:

  • This Backdoor 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)

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

15.510.02

FIRST VSAPI PATTERN DATE:

21 Nov 2019

VSAPI OPR PATTERN File:

15.511.00

VSAPI OPR PATTERN Date:

22 Nov 2019

Step 1

Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:

    Troj.Win32.TRX.XXPE50FFF033

Step 2

Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.

Step 3

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 4

Restart in Safe Mode

[ Learn More ]

Step 5

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows
    • Load = "%User Profile%\OEM\systeminfo.exe"

Step 6

Delete this registry key

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • HKEY_CURRENT_USER\Software\Remcos-{random}

Step 7

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %Application Data%\remcos
  • %User Profile%\OEM

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Backdoor.MSIL.REMCOS.AOJ. 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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