Author: Maria Emreen Viray   

 

Ransom:Win32/Conti.ZA (MICROSOFT)

 PLATFORM:

Windows

 OVER ALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE
Low
Medium
High
Critical

  • Threat Type:
    Ransomware

  • Destructiveness:
    No

  • Encrypted:
    Yes

  • 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: 200,704 bytes
File type: EXE
Memory resident: Yes
INITIAL SAMPLES RECEIVED DATE: 07 июля 2021
PAYLOAD: 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 drops the following files:

  • {Log File Path}\{Log Filename} → If -log argument is used

It adds the following processes:

  • cmd.exe /c C:\Windows\System32\wbem\WMIC.exe shadowcopy where "ID='{Shadowcopy ID}'" delete → repeated depending on the number of shadow copies

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • YUIOGHJKCVVBNMFGHJKTYQUWIETASKDHGZBDGSKL237782321344

Other Details

This Ransomware does the following:

  • It uses the Windows Restart Manager to unlock files it will encrypt.
  • When encrypting network shares it will check if the IP address starts with the following to ensure that it is encrypting local, non-Internet, systems:
    • 172.
    • 192.168.
    • 10.
    • 169.
  • It accepts the following parameters:
    • -m {all|local|net|backups}
    • all - combination of net and local
    • local - delete backups and encrypt only locally found drives
    • net - delete backups and encrypt only network shares
    • backups - delete backups
    • -p {Directory} - Will encrypt first the folders in the list before proceeding to the others
    • -log {Log File Path}\{Log Filename} - Log output to {Log File Path}\{Log Filename}
    • -nomutex - Creates no mutex allowing multiple process
    • -size {chunk mode}
  • By default, it encrypts local drives, removable drives and network shares

Ransomware Routine

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

  • readme.txt
  • CONTI_LOG.txt

It avoids encrypting files with the following strings in their file path:

  • tmp
  • winnt
  • temp
  • thumb
  • $Recycle.Bin
  • $RECYCLE.BIN
  • System Volume Information
  • Boot
  • Windows
  • Trend Micro
  • Perflogs

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

  • .PSFUX

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:

  • .PSFUX
  • .exe
  • .dll
  • .lnk
  • .sys
  • .msi
  • .bat

  SOLUTION

Minimum scan engine: 9.800
First VSAPI Pattern File: 16.870.07
First VSAPI Pattern Release Date: 28 июля 2021
VSAPI OPR PATTERN-VERSION: 16.871.00
VSAPI OPR PATTERN DATE: 29 июля 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:

     
    • Troj.Win32.TRX.XXPE50FFF046

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 this file

[ learnMore ]
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.
  • {Log File Path}\{Log Filename}
  • {Encrypted Directory}\readme.txt

Step 5

Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.CONTI.FAJF. 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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