Backdoor.Win32.REMCOS.YABCR

May 06, 2021
 Analysis by: Thea Patrice Tajonera
 ALIASES:

Trojan:Win32/Bladabindi.BA!MTB (MICROSOFT); Trojan-Spy.FormBook (IKARUS)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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.

  TECHNICAL DETAILS

File Size:

753,467 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

18 Mar 2021

Payload:

Connects to URLs/IPs, Collects system information, Steals information

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 the following copies of itself into the affected system:

  • %Application Data%\IDMComp\UltraEdit\autorec\SyncHost.exe

(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 files:

  • %User Temp%\Takeup
  • %User Temp%\SpanielPolymorph.dll
  • %User Temp%\{Random Characters}.lnk -> points to %Application Data%\IDMComp\UltraEdit\autorec\SyncHost.exe
  • %Windows%\Tasks\SyncHost.job
  • %Application Data%\remcos\logs.dat -> contains the stolen information

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

It drops the following non-malicious files:

  • %User Temp%\releases\bot-trap\glimpse\delegates.xml
  • %User Temp%\releases\bot-trap\glimpse\kbarticle.xml
  • %User Temp%\releases\bot-trap\glimpse\x-cobol.xml
  • %User Temp%\releases\bot-trap\glimpse\clstencilui.dll
  • %User Temp%\releases\bot-trap\glimpse\sbsVsaVb7rt.dll
  • %User Temp%\releases\bot-trap\glimpse\org.gnome.Logs.gschema.xml
  • %User Temp%\magazine\arts\crtowordsde.dll
  • %User Temp%\magazine\arts\dumpbin.exe
  • %User Temp%\magazine\arts\vswebdesignedui.dll
  • %User Temp%\m\remote-browser.xml
  • %User Temp%\m\tcprops.dll
  • %User Temp%\cv\24.opends60.dll
  • %User Temp%\cv\sqlleUI.dll
  • %User Temp%\cv\DbgUrtMnu.dll
  • %User Temp%\cv\pgort80ui.dll
  • %User Temp%\cv\spro5000.xml
  • %User Temp%\cv\iptables-xml
  • %User Temp%\cv\gif.xml
  • %User Temp%\cv\ConmanClient2.exe
  • %User Temp%\zoom\02\ConmanClient2.exe
  • %User Temp%\zoom\02\x-pagemaker.xml

(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 processes:

  • %System%\rundll32.exe TubeHygrostat,Xerophytes
  • "%System%\cmd.exe"

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

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

  • Mutex_RemWatchdog
  • Remcos_Mutex_Inj

Other System Modifications

This Backdoor adds the following registry entries:

HKEY_CURRENT_USER\Software\Remcos-YAKX39
exepath = {Hex Values}

HKEY_CURRENT_USER\Software\Remcos-YAKX39
licence = {Hex Values}

Backdoor Routine

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

  • Open and Close Camera
  • Download and Upload Files
  • Enumerate Files
  • Execute Files
  • Delete Files
  • Rename Files
  • Change File Attributes
  • Start and Stop Keylogger
  • Retrieve and Clear login data and cookies from the following web browsers:
    • Google Chrome
    • Mozilla Firefox
    • Internet Explorer
  • Play, Pause, and Stop an Alarm
  • Play, Pause, Stop, and Record Audio
  • Change Desktop Wallpaper
  • Enumerate Running Processes
  • Create and Terminate Processes
  • Manage Registry Keys and Entries (Create, Enumerate, Modify, and Delete)
  • Manage Services (Create, Enumerate, Modify, Start, Stop, and Delete)
  • Create Image
  • Save Image
  • Screen Capture user's desktop
  • Set, Copy, and Clear Clipboard Data
  • Restarts the affected machine
  • Sleeps the affected machine
  • Logs off the affected machine
  • Shutdown the affected machine
  • Pop-up a Messagebox

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

  • veintiunoremco.{BLOCKED}s.org

Information Theft

This Backdoor gathers the following data:

  • Computer Name
  • Username
  • Windows Architecture (32-bit or 64-bit)
  • Locale Info
  • User Privileges (Admin or not)
  • Clipboard Data
  • Keyboard Input
  • Mouse Activity
  • User Keystrokes
  • User Activity (Idle Time)
  • Memory Information
  • System Drive Information

Other Details

This Backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\Remcos-YAKX39

It does the following:

  • This Backdoor changes the file attributes of its dropped file to Hidden

It adds the following scheduled tasks:

  • Name: SyncHost
    Trigger: After triggered, repeat every 00:04:00 for a duration of 1 day
    Action: Start a program %Application Data%\IDMComp\UltraEdit\autorec\SyncHost.exe

(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).)

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

16.606.08

FIRST VSAPI PATTERN DATE:

20 Mar 2021

VSAPI OPR PATTERN File:

16.607.00

VSAPI OPR PATTERN Date:

21 Mar 2021

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.XXPE50FSX008

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

Deleting Scheduled Tasks

The following {Task Name} - {Task to be run} listed should be used in the steps identified below:

{SyncHost} - {%Application Data%\IDMComp\UltraEdit\autorec\SyncHost.exe}

For Windows 2000, Windows XP, and Windows Server 2003:

  1. Open the Windows Scheduled Tasks. Click Start>Programs>Accessories>
    System Tools>Scheduled Tasks.
  2. Locate each {Task Name} values listed above in the Name column.
  3. Right-click on the said file(s) with the aforementioned value.
  4. Click on Properties. In the Run field, check for the listed {Task to be run}.
  5. If the strings match the list above, delete the task.

For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:

  1. Open the Windows Task Scheduler. To do this:
    • On Windows Vista, Windows 7, and Windows Server 2008, click Start, type taskschd.msc in the Search input field, then press Enter.
    • On Windows 8, Windows 8.1, and Windows Server 2012, right-click on the lower left corner of the screen, click Run, type taskschd.msc, then press Enter.
  2. In the left panel, click Task Scheduler Library.
  3. In the upper-middle panel, locate each {Task Name} values listed above in the Name column.
  4. In the lower-middle panel, click the Actions tab. In the Details column, check for the {Task to be run} string.
  5. If the said string is found, delete the task.

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\Remcos-YAKX39
    • exepath = {Hex Values}
  • In HKEY_CURRENT_USER\Software\Remcos-YAKX39
    • licence = {Hex Values}

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-YAKX39

Step 7

Search and delete this file

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %Application Data%\IDMComp\UltraEdit\autorec\SyncHost.exe
  • %User Temp%\releases\bot-trap\glimpse\delegates.xml
  • %User Temp%\releases\bot-trap\glimpse\kbarticle.xml
  • %User Temp%\releases\bot-trap\glimpse\x-cobol.xml
  • %User Temp%\releases\bot-trap\glimpse\clstencilui.dll
  • %User Temp%\releases\bot-trap\glimpse\sbsVsaVb7rt.dll
  • %User Temp%\releases\bot-trap\glimpse\org.gnome.Logs.gschema.xml
  • %User Temp%\magazine\arts\crtowordsde.dll
  • %User Temp%\magazine\arts\dumpbin.exe
  • %User Temp%\magazine\arts\vswebdesignedui.dll
  • %User Temp%\m\remote-browser.xml
  • %User Temp%\m\tcprops.dll
  • %User Temp%\cv\24.opends60.dll
  • %User Temp%\cv\sqlleUI.dll
  • %User Temp%\cv\DbgUrtMnu.dll
  • %User Temp%\cv\pgort80ui.dll
  • %User Temp%\cv\spro5000.xml
  • %User Temp%\cv\iptables-xml
  • %User Temp%\cv\gif.xml
  • %User Temp%\cv\ConmanClient2.exe
  • %User Temp%\zoom\02\ConmanClient2.exe
  • %User Temp%\zoom\02\x-pagemaker.xml
  • %User Temp%\Takeup
  • %User Temp%\SpanielPolymorph.dll
  • %User Temp%\{Random Characters}.lnk
  • %Windows%\Tasks\SyncHost.job
  • %Application Data%\remcos\logs.dat

Step 8

Scan your computer with your Trend Micro product to delete files detected as Backdoor.Win32.REMCOS.YABCR. 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 the following Trend Micro Support pages for more information:


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