kraken_cryptor_ransomware_loader

YARA-2025-2154 Critical general Active

Rule to detect the Kraken Cryptor Ransomware loader

kraken_cryptor_ransomware_loader.yar Valid Syntax
rule kraken_cryptor_ransomware_loader {

   meta:

      description = "Rule to detect the Kraken Cryptor Ransomware loader"
      author = "Marc Rivero | McAfee ATR Team"
	  reference = "https://securingtomorrow.mcafee.com/mcafee-labs/fallout-exploit-kit-releases-the-kraken-ransomware-on-its-victims/"
   strings:

      $pdb = "C:\\Users\\Krypton\\source\\repos\\UAC\\UAC\\obj\\Release\\UAC.pdb" fullword ascii
      $s2 = "SOFTWARE\\Classes\\mscfile\\shell\\open\\command" fullword wide
      $s3 = "public_key" fullword ascii
      $s4 = "KRAKEN DECRYPTOR" ascii
      $s5 = "UNIQUE KEY" fullword ascii


   condition:

      ( uint16(0) == 0x5a4d and filesize < 600KB ) and $pdb or all of ($s*)
}

rule kraken_cryptor_ransomware {
   
   meta:

      description = "Rule to detect the Kraken Cryptor Ransomware"
      author = "Marc Rivero | McAfee ATR Team"
	  reference = "https://securingtomorrow.mcafee.com/mcafee-labs/fallout-exploit-kit-releases-the-kraken-ransomware-on-its-victims/"

   strings:
     
      $s1 = "Kraken Cryptor" fullword ascii nocase
      $s2 = "support_email" fullword ascii
      $fw1 = "L0MgbmV0c2ggYWR2ZmlyZXdhbGwgZmlyZXdhbGwgYWRkIHJ1bGUgbmFtZT0iU01CIFByb3RvY29sIEJsb2NrIiBwcm90b2NvbD1UQ1AgZGlyPWluIGxvY2FscG9ydD00" ascii 
      $fw2 = "L0MgbmV0c2ggYWR2ZmlyZXdhbGwgZmlyZXdhbGwgYWRkIHJ1bGUgbmFtZT0iUkRQIFByb3RvY29sIEJsb2NrIiBwcm90b2NvbD1UQ1AgZGlyPWluIGxvY2FscG9ydD0z" ascii 
      $fw3 = "L0MgbmV0c2ggYWR2ZmlyZXdhbGwgZmlyZXdhbGwgYWRkIHJ1bGUgbmFtZT0iUkRQIFByb3RvY29sIEJsb2NrIiBwcm90b2NvbD1UQ1AgZGlyPWluIGxvY2FscG9ydD0z" ascii 
      $fw4 = "L0MgbmV0c2ggYWR2ZmlyZXdhbGwgZmlyZXdhbGwgYWRkIHJ1bGUgbmFtZT0iU01CIFByb3RvY29sIEJsb2NrIiBwcm90b2NvbD1UQ1AgZGlyPWluIGxvY2FscG9ydD00" ascii 
      $uac = "<!--<requestedExecutionLevel level=\"asInvoker\" uiAccess=\"false\" />-->   " fullword ascii
  
   condition:

      ( uint16(0) == 0x5a4d and filesize < 600KB ) and all of ($fw*) or all of ($s*) or $uac
}

rule ransom_note_kraken_cryptor_ransomware {
   
   meta:

      description = "Rule to detect the ransom note delivered by Kraken Cryptor Ransomware"
      author = "Marc Rivero | McAfee ATR Team"
	  reference = "https://securingtomorrow.mcafee.com/mcafee-labs/fallout-exploit-kit-releases-the-kraken-ransomware-on-its-victims/"

   strings:

      $s1 = "No way to recovery your files without \"KRAKEN DECRYPTOR\" software and your computer \"UNIQUE KEY\"!" fullword ascii
      $s2 = "Are you want to decrypt all of your encrypted files? If yes! You need to pay for decryption service to us!" fullword ascii
      $s3 = "The speed, power and complexity of this encryption have been high and if you are now viewing this guide." fullword ascii
      $s4 = "Project \"KRAKEN CRYPTOR\" doesn't damage any of your files, this action is reversible if you follow the instructions above." fullword ascii
      $s5 = "https://localBitcoins.com" fullword ascii
      $s6 = "For the decryption service, we also need your \"KRAKEN ENCRYPTED UNIQUE KEY\" you can see this in the top!" fullword ascii
      $s7 = "-----BEGIN KRAKEN ENCRYPTED UNIQUE KEY----- " fullword ascii
      $s8 = "All your files has been encrypted by \"KRAKEN CRYPTOR\"." fullword ascii
      $s9 = "It means that \"KRAKEN CRYPTOR\" immediately removed form your system!" fullword ascii
      $s10 = "After your payment made, all of your encrypted files has been decrypted." fullword ascii
      $s11 = "Don't delete .XKHVE files! there are not virus and are your files, but encrypted!" fullword ascii
      $s12 = "You can decrypt one of your encrypted smaller file for free in the first contact with us." fullword ascii
      $s13 = "You must register on this site and click \"BUY Bitcoins\" then choose your country to find sellers and their prices." fullword ascii
      $s14 = "-----END KRAKEN ENCRYPTED UNIQUE KEY-----" fullword ascii
      $s15 = "DON'T MODIFY \"KRAKEN ENCRYPT UNIQUE KEY\"." fullword ascii
      $s16 = "# Read the following instructions carefully to decrypt your files." fullword ascii
      $s17 = "We use best and easy way to communications. It's email support, you can see our emails below." fullword ascii
      $s18 = "DON'T USE THIRD PARTY, PUBLIC TOOLS/SOFTWARE TO DECRYPT YOUR FILES, THIS CAUSE DAMAGE YOUR FILES PERMANENTLY." fullword ascii
      $s19 = "https://en.wikipedia.org/wiki/Bitcoin" fullword ascii
      $s20 = "Please send your message with same subject to both address." fullword ascii
   condition:

      ( uint16(0) == 0x4120 and filesize < 9KB ) and all of them 
}

Rule Metadata

description
Rule to detect the Kraken Cryptor Ransomware loader
author
Marc Rivero | McAfee ATR Team
reference
https://securingtomorrow.mcafee.com/mcafee-labs/fallout-exploit-kit-releases-the-kraken-ransomware-on-its-victims/

String Definitions

{"name":"$pdb","value":"\"C:\\\\Users\\\\Krypton\\\\source\\\\repos\\\\UAC\\\\UAC\\\\obj\\\\Release\\\\UAC.pdb\" fullword ascii"}
{"name":"$s2","value":"\"SOFTWARE\\\\Classes\\\\mscfile\\\\shell\\\\open\\\\command\" fullword wide"}
{"name":"$s3","value":"\"public_key\" fullword ascii"}
{"name":"$s4","value":"\"KRAKEN DECRYPTOR\" ascii"}
{"name":"$s5","value":"\"UNIQUE KEY\" fullword ascii"}

Threat Analysis

This YARA rule is designed to detect general threats.

Severity Level: Critical

The rule uses pattern matching to identify specific byte sequences, strings, or behavioral patterns associated with malicious activity.

Detection Capabilities

  • File-based detection for executables and documents
  • Memory scanning for running processes
  • Network traffic analysis support

Command Line Usage

# Scan a single file
yara kraken_cryptor_ransomware_loader.yar /path/to/suspicious/file

# Scan a directory recursively
yara -r kraken_cryptor_ransomware_loader.yar /path/to/directory/

# Scan with metadata output
yara -m kraken_cryptor_ransomware_loader.yar target_file

# Scan process memory (Linux)
yara kraken_cryptor_ransomware_loader.yar /proc/[pid]/exe

Integration Examples

Python (yara-python)

import yara
rules = yara.compile(filepath='kraken_cryptor_ransomware_loader.yar')
matches = rules.match('/path/to/file')

ClamAV Integration

clamscan --yara-rules=kraken_cryptor_ransomware_loader.yar /path/to/scan

Rule Information

YARA ID
YARA-2025-2154
Created
August 19, 2025
Last Updated
August 19, 2025
Last Imported
Never

Threat Intelligence

Risk Level Critical
Category general
Detection Confidence Analysis Pending
False Positive Rate Not Available
Last Seen in Wild No Data

Export Options