Analysis by: Nathaniel Gregory Ragasa
ALIASES:

Win32:RansomX-gen [Ransom](AVAST)

 PLATFORM:

Windows

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

  • Threat Type: Ransomware

  • Destructiveness: No

  • Encrypted: No

  • 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.

However, as of this writing, the said sites are inaccessible.

It encrypts files found in specific folders. It drops files as ransom note.

  TECHNICAL DETAILS

File Size: 12,800 bytes
File Type: EXE
Memory Resident: No
Payload: Connects to URLs/IPs, Drops 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.

Installation

This Ransomware adds the following processes:

  • "%System%\NOTEPAD.EXE" %Desktop%\HOW TO GET YOUR FILES BACK.TXT

(Note: %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\Desktop on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)

Download Routine

This Ransomware connects to the following URL(s) to download its component file(s):

  • http://{BLOCKED}.{BLOCKED}.115.94/zambos_caldo_de_p.txt

Other Details

However, as of this writing, the said sites are inaccessible.

Ransomware Routine

This Ransomware encrypts files found in the following folders:

  • Documents
  • Downloads
  • Pictures
  • Desktop
  • Videos
  • {All Drive} - except System Drives

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

  • .khonsari

It drops the following file(s) as ransom note:

  • %Destop%\HOW TO GET YOUR FILES BACK.TXT

  SOLUTION

Minimum Scan Engine: 9.800
FIRST VSAPI PATTERN FILE: 17.252.07
FIRST VSAPI PATTERN DATE: 14 Dec 2021
VSAPI OPR PATTERN File: 17.253.00
VSAPI OPR PATTERN Date: 15 Dec 2021

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:

     
    • WORM.Win32.TRX.XXPE50FFF051

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

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.
  • %Destop%\HOW TO GET YOUR FILES BACK.TXT

Step 5

Scan your computer with your Trend Micro product to delete files detected as Ransom.MSIL.KHONSARI.YXBLN. 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 6

Restore encrypted files from backup.


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