Ransom.Linux.MONTI.THGOCBC

August 24, 2023
 Analysis by: Carlos Villegas Madrid
 ALIASES:

ELF:Filecoder-FB [Ransom] (AVAST)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It avoids encrypting files with the following file extensions.

  TECHNICAL DETAILS

File Size:

1,464,144 bytes

File Type:

ELF

Memory Resident:

No

Initial Samples Received Date:

03 Jul 2023

Payload:

Encrypts files

Arrival Details

This Ransomware arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Other Details

This Ransomware does the following:

  • It encrypts all files except for the avoided filename and extension.
  • It modifies the contents of the following and replaces the ransomnote text:
    • "/etc/motd"
    • "/usr/lib/vmware/hostd/docroot/index.html"

It accepts the following parameters:

  • --path Path to file (required) [--path /vmfs/volumes]
  • --whitelist List of VM's that i need to skip [--whitelist /wltxt]
  • --vmkill Whether to kill the virtual machine
  • --detach Detach from the screen

Ransomware Routine

This Ransomware avoids encrypting files with the following strings in their file name:

  • readme.txt

It appends the following extension to the file name of the encrypted files:

  • .monti

It leaves text files that serve as ransom notes containing the following text:

  • {Encrypted Directory}\readme.txt

It avoids encrypting files with the following file extensions:

  • .monti
  • .sf

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

18.546.03

FIRST VSAPI PATTERN DATE:

03 Jul 2023

VSAPI OPR PATTERN File:

18.547.00

VSAPI OPR PATTERN Date:

04 Jul 2023

Step 1

Scan your computer with your Trend Micro product to delete files detected as Ransom.Linux.MONTI.THGOCBC. 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:

Step 2

Restore encrypted files from backup.


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