Analysis by: John Rey Canon

ALIASES:

Backdoor.Win32.Remcos.jef (Kaspersky); Trojan.TR/AD.Remcos.yntfd (F-Secure); Win32.Backdoor.Remcos.Egyh (Tencent)

 PLATFORM:

Windows

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

  • 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

File Size: 1,231,360 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 25 Sep 2019

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 files:

  • %System Root%\{Computer Name}\TieringEngineService\GameBarPresenceWriter.exe
  • %User Startup%\TieringEngineService.lnk
  • %Application Data%\remcos\logs.dat

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows 2003(32-bit), XP and 2000(32-bit), or C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit), 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 creates the following folders:

  • %System Root%\{Computer Name}
  • %System Root%\{Computer Name}\TieringEngineService
  • %Application Data%\remcos

(Note: %System Root% is the Windows root folder, where it usually is C:\ 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).)

Other System Modifications

This Backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\Remcos-{Random String}
exepath = ""

HKEY_CURRENT_USER\Software\Remcos-{Random String}
licence = ""

HKEY_CURRENT_USER\Software
Remcos-{Random String} = ""

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Remcos-{Random String}
exepath = {Encrypted Data}

HKEY_CURRENT_USER\Software\Remcos-{Random String}
licence = {GUID}

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 15.392.04
FIRST VSAPI PATTERN DATE: 26 Sep 2019
VSAPI OPR PATTERN File: 15.393.00
VSAPI OPR PATTERN Date: 27 Sep 2019

Step 1

Trend Micro products with the XGen technology detect this malware as

[ Learn More ]

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

Identify and terminate files detected as Backdoor.AutoIt.REMCOS.USMANEAGDC

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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-{Random String}
    • exepath = {Encrypted Data}
  • In HKEY_CURRENT_USER\Software\Remcos-{Random String}
    • licence = {GUID}

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.

  • In HKEY_CURRENT_USER\Software
    • Remcos-{Random String} = ""

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.
  • %System Root%\{Computer Name}\TieringEngineService\GameBarPresenceWriter.exe
  • %User Startup%\TieringEngineService.lnk
  • %Application Data%\remcos\logs.dat

Step 8

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.
  • %System Root%\{Computer Name}\TieringEngineService
  • %System Root%\{Computer Name}
  • %Application Data%\remcos

Step 9

Scan your computer with your Trend Micro product to delete files detected as Backdoor.AutoIt.REMCOS.USMANEAGDC. 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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