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Backdoor.Win32.COBEACON.OSLJAI

November 17, 2020
 Analysis by: Arianne Grace Dela Cruz
 ALIASES:

Gen:Variant.Bulz.1217(BITDEFENDER); BScope.Trojan.Swrort (VBA32)

 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

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:

97,792 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

13 Nov 2020

Payload:

Connects to URLs/IPs, 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 adds the following processes:

  • cmd.exe /c set KCBDaOagLE=6566 & reg add HKCU\SOFTWARE\mfSHHuXxjQrzxcR /v plTQxPKiomXOVqV /t REG_DWORD /d 5868 & exit

Other System Modifications

This Backdoor adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\SOFTWARE\mfSHHuXxjQrzxcR
plTQxPKiomXOVqV = 5868

Backdoor Routine

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

  • Manage Files (Create, Delete, Modify, List files in Directory, Copy Files, Move Files)
  • Manage Directory (Create, Set path)
  • Read/Modify file time
  • Manage Services (Create, Delete, Start)
  • Impersonate Tokens
  • Open Processes and obtain process information
  • Inject Code to Processes
  • Adjust permissions in process
  • Connect to a named pipe
  • Retrieve IP Address mapping table
  • Create, Terminate, and List Running Processes
  • List Drive Information
  • Enumerate Registry Data
  • Executes arbitrary code

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

  • http://{BLOCKED}.{BLOCKED}.194.115/pixel.gif

Information Theft

This Backdoor gathers the following data:

  • User Name
  • Computer Name
  • Host Name
  • Local IP Address
  • OS Version and Architecture
  • Current Process ID

Other Details

This Backdoor does the following:

  • It connects to the following URL to download an encrypted DLL component which it will load in its memory:
    • http://{BLOCKED}.{BLOCKED}.194.115/E4lw
  • It adds the following environment variable and value:
    • KCBDaOagLE= 6566

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

16.356.03

FIRST VSAPI PATTERN DATE:

17 Nov 2020

VSAPI OPR PATTERN File:

16.357.00

VSAPI OPR PATTERN Date:

18 Nov 2020

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.XXPE50FFF038

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\mfSHHuXxjQrzxcR
    • plTQxPKiomXOVqV = 5868

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Backdoor.Win32.COBEACON.OSLJAI. 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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