Backdoor.MSIL.REMCOS.TIOIBEGO
Windows
Threat Type: Backdoor
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
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.
TECHNICAL DETAILS
314572800 bytes
EXE
Yes
31 Jan 2023
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%\splt\splt.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:
- %Application Data%\splt\splt.exe
- %ProgramData%\remcos\logs.dat
- %Temp%\AEI{4 random values}.tmp → deleted afterwards
(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).. %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This contains application data for all users. This is usually C:\ProgramData on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit), or C:\Documents and Settings\All Users on Windows Server 2003(32-bit), 2000(32-bit) and XP.. %Temp% is the Windows temporary folder, where it usually is C:\Windows\Temp on all Windows operating system versions.)
It adds the following processes:
- %Windows%\Microsoft.NET\Framework\v4.0.30319\csc.exe
- "cmd" /c mkdir "%Application Data%\splt"
- "cmd" /c schtasks /create /sc minute /mo 1 /tn "Nafifas" /tr "'%Application Data%\splt\splt.exe'" /f
- "cmd" /c copy "{Malware Path}\{Malware Filename}.exe" "%Application Data%\splt\splt.exe"
(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.. %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 creates the following folders:
- %Application Data%\splt
(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).)
Other System Modifications
This Backdoor adds the following registry keys as part of its installation routine:
HKEY_CURRENT_USER\Software\Rmc-FYTY80
It also creates the following registry entry(ies) as part of its installation routine:
HKEY_CURRENT_USER\Software\Rmc-FYTY80
exepath = {Hex Values}
HKEY_CURRENT_USER\Software\Rmc-FYTY80
licence = 664E563EC8C93F9B2417F07269DA1924
Other Details
This Backdoor connects to the following possibly malicious URL:
- {BLOCKED}.{BLOCKED}.{BLOCKED}.{BLOCKED}:9000 → using TCP
It adds the following scheduled tasks:
- Name: Nafifas
Trigger: After triggered, repeat every 00:01:00 indefinitely
Action: Start the program %Application Data%\splt\splt.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
9.800
18.286.08
01 Mar 2023
18.287.00
02 Mar 2023
Step 1
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 2
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 3
Restart in Safe Mode
Step 4
Deleting Scheduled Tasks while in Safe Mode
- Still in safe mode, the following {Task Name}-{Task to be run} listed should be used in the steps identified below: DATA_GENERIC
- For Windows 7 and Server 2008 (R2) users, click Start>Computer.
- For Windows 8, 8.1, 10, and Server 2012 users, right-click on the lower left corner of the screen, then click File Explorer.
- In the Search Computer/This PC input box, type:
- %System%\Tasks\{Task Name}
- Once located, select the file then press SHIFT+DELETE to delete it.
- Open Registry Editor. To do this:
- For Windows 7 and Server 2008 (R2) users, click the Start button, type regedit in the Search input field, and press Enter.
- For Windows 8, 8.1, 10, and Server 2012 (R2) users, right-click on the lower left corner of the screen, click Run, type regedit in the text box
- In the left panel of the Registry Editor window, double-click the following:
- HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Schedule>TaskCache>Tree>{Task Name}
- Locate the created entry and take note of the registry value's data:
- ID={Task Data}
- After taking note of the data, delete the registry key:
- HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Schedule>TaskCache>Tree>{Task Name}
- In the left panel of the Registry Editor window, double-click the following:
- HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Schedule>TaskCache>Tasks
- Still in the left panel, locate and delete the registry key with the same name as the located Task Data in step #6:
- ={Task Data}
- Close Registry Editor.
Step 5
Delete this registry key
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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.
- In HKEY_CURRENT_USER\Software\Rmc-FYTY80
Step 6
Search and delete this file
- %Application Data%\splt\splt.exe
- %ProgramData%\remcos\logs.dat
- %Temp%\AEI{4 random values}.tmp
Step 7
Search and delete these folders
- %Application Data%\splt
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as Backdoor.MSIL.REMCOS.TIOIBEGO. 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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