Analysis by: Arvin Roi Macaraeg

ALIASES:

Trojan.Win32.BypassUAC.dj(KASPERSKY); Trojan:Win32/Occamy.C(Microsoft)

 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: 1,218,048 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 17 Jul 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 creates the following folders:

  • %Application Data%\test1
  • %AppDataLocal%\bfrbtpRAR
  • %Application Data%\bfrbtpCache

(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).. %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 injects codes into the following process(es):

  • notepad.exe

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
bfrbtp = %AppDataLocal%\bfrbtpRAR\bfrbtp.vbs

Other System Modifications

This Backdoor adds the following registry entries:

HKEY_CURRENT_USER\Software\Remcos-VWO2FV
exepath = {Hex Values}

HKEY_CURRENT_USER\Software\Remcos-VWO2FV
licence = {Random values}

Dropping Routine

This Backdoor drops the following files:

  • %AppDataLocal%\bfrbtpRAR\bfrbtp.bmp
  • %Application Data%\bfrbtpCache\bfrbtpytx.exe
  • %AppDataLocal%\bfrbtpRAR\bfrbtp.ocx
  • %AppDataLocal%\bfrbtpRAR\bfrbtpN.vbs
  • %AppDataLocal%\bfrbtpRAR\bfrbtp.vbs
  • %Application Data%\test1\logs.dat

(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).. %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 Details

This Backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.239.14:2980

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 15.240.05
FIRST VSAPI PATTERN DATE: 17 Jul 2019
VSAPI OPR PATTERN File: 15.241.01
VSAPI OPR PATTERN Date: 18 Jul 2019

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

Identify and terminate files detected as Backdoor.Win32.REMCOS.JKPA

[ 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 3

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-VWO2FV
    • exepath = {Hex Values}
  • In HKEY_CURRENT_USER\Software\Remcos-VWO2FV
    • licence = {Random Values}

Step 4

Search and delete these files

[ 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.
  • %AppDataLocal%\bfrbtpRAR\bfrbtp.bmp
  • %Application Data%\bfrbtpCache\bfrbtpytx.exe
  • %AppDataLocal%\bfrbtpRAR\bfrbtp.ocx
  • %AppDataLocal%\bfrbtpRAR\bfrbtpN.vbs
  • %AppDataLocal%\bfrbtpRAR\bfrbtp.vbs
  • %Application Data%\test1\logs.dat

Step 5

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%\test1
  • %AppDataLocal%\bfrbtpRAR
  • %Application Data%\bfrbtpCache

Step 6

Scan your computer with your Trend Micro product to delete files detected as Backdoor.Win32.REMCOS.JKPA. 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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