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
Repository
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
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